Sec Form 4 Filing - VASSALLUZZO SCOTT J @ SEI INVESTMENTS CO - 2005-12-15

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 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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1. Name and Address of Reporting Person VASSALLUZZO SCOTT J 2. Issuer Name and Ticker or Trading Symbol SEI INVESTMENTS CO [ SEIC] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) X __ Other (specify below) Member of Section 13(d) Group (Last) (First) (Middle) 323 RAILROAD AVENUE 3. Date of Earliest Transaction (MM/DD/YY) 12/15/2005 (Street) GREENWICH, CT06830 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ 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 (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 12/15/2005 S 35,000 D $ 38.6 199,100 I ( 1 ) By Prescott Investors Profit Sharing Trust

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 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 VASSALLUZZO SCOTT J 323 RAILROAD AVENUE GREENWICH, CT06830 X Member of Section 13(d) Group PRESCOTT INVESTORS PROFIT SHARING TRUST 323 RAILROAD AVENUE GREENWICH, CT06830 Member of Section 13(d) Group Signatures /s/ Scott J. Vassalluzzo, individually and as trustee of Prescott Investors Profit Sharing Trust 12/16/2005 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares sold in this transaction were owned directly by Prescott Investors Profit Sharing Trust (the "Trust") and indirectly by Scott J. Vassalluzzo as a trustee of the Trust. Mr. Vassalluzzo disclaims beneficial ownership of these shares in excess of his pencuniary interest under 16a-8(b)(2)(ii). The address for the Trust is 323 Railroad Avenue, Greenwich, CT 06830

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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