Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
WEST ALFRED P JR
   2. Issuer Name and Ticker or Trading Symbol
SEI INVESTMENTS CO [SEIC] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
__X__ Director __X__ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
Chairman and Chief Executive
(Last)
(First)
(Middle)
ONE FREEDOM VALLEY DRIVE		 3. Date of Earliest Transaction (Month/Day/Year)
10/21/2005
(Street)

OAKS, PA 19456		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 10/21/2005   S   15,000 D $ 37.8 10,931,033 D  
Common Stock 10/21/2005   S   3,150 D $ 37.8 10,927,883 D  
Common Stock 10/21/2005   S   6,835 D $ 37.81 10,921,048 D  
Common Stock 10/21/2005   S   350 D $ 37.82 10,920,698 D  
Common Stock 10/21/2005   S   479 D $ 37.83 10,920,219 D  
Common Stock 10/21/2005   S   300 D $ 37.84 10,919,919 D  
Common Stock 10/21/2005   S   5,000 D $ 37.84 10,914,919 D  
Common Stock 10/21/2005   S   172 D $ 37.85 10,914,747 D  
Common Stock 10/21/2005   S   50 D $ 37.86 10,914,697 D  
Common Stock 10/21/2005   S   50 D $ 37.87 10,914,647 D  
Common Stock 10/21/2005   S   433 D $ 37.88 10,914,214 D  
Common Stock 10/21/2005   S   145 D $ 37.89 10,914,069 D  
Common Stock 10/21/2005   S   250 D $ 37.9 10,913,819 D  
Common Stock 10/21/2005   S   350 D $ 37.91 10,913,469 D  
Common Stock 10/21/2005   S   23 D $ 37.92 10,913,446 D  
Common Stock 10/21/2005   S   127 D $ 37.93 10,913,319 D  
Common Stock 10/21/2005   S   150 D $ 37.94 10,913,169 D  
Common Stock 10/21/2005   S   4,000 D $ 37.95 10,909,169 D  
Common Stock 10/21/2005   S   1,400 D $ 37.96 10,907,769 D  
Common Stock 10/21/2005   S   600 D $ 37.97 10,907,169 D  
Common Stock               24,000 I By Wife
Common Stock               4,537,000 I By APWest Associates, LP (1)
Common Stock               246,298 I By 1980 Minority Trust - Alfred P. West, III (2)
Common Stock               1,398,000 I By 1980 Life Trust - Alfred P. West III (2)
Common Stock               1,405,295 I By 1980 Life Trust - Andrew Palmer West (2)
Common Stock               1,400,735 I By 1980 Life Trust - Angela Paige West (2)
Common Stock               2,118 I By Residuary Trust (3)
Common Stock               32,197 I By the Marital Trust (GST Exempt) (4)
Common Stock               32,377 I By the Marital Trust (Non-GST Exempt) (4)
Common Stock               32,200 I By West Senior Securities Fund, L.P.

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
WEST ALFRED P JR
ONE FREEDOM VALLEY DRIVE
OAKS, PA 19456		   X   X   Chairman and Chief Executive  

Signatures

 Ruth A. Montgomery (Attorney-in-fact)   10/25/2005
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) Mr. West disclaims beneficial ownership of the shares held by AP West Associates, L.P., except to the extent of his pecuniary interest therein.
(2) These shares are held in trusts for the benefit of Mr. West's children. Mr. West's wife is the trustee or a co-trustee of these trusts. Mr. West disclaims beneficial ownership of the shares held in these trusts.
(3) The trust that holds these shares (the "Residuary Trust") is for the benefit of Mr. West's mother and certain descendants of Mr. West's father. The Residuary Trust was created upon the death of Mr. West's father under the terms of an existing trust that Mr. West's father had established prior to his death. In connection with the establishment of the Residuary Trust, Mr. West became the trustee of the Residuary Trust in September 2002. Mr. West disclaims beneficial ownership of the shares held by the Residuary Trust, except to the extent of his pecuniary interest therein.
(4) Mr. West is the trustee of the Marital Trusts (GST and non-GST exempt), which hold shares for the benefit of Mr. West's mother.

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