0001036050-01-500333 DEF 14A 1 20010529 20010423 SEI CORP 0000350894 6211 231707341 PA 1231 DEF 14A 34 000-10200 1608604 1 FREEDOM VALLEY DRIVE OAKS PA 19456-1100 6106761000 1 FREEDOM VALLEY DRIVE OAKS PA 19456-1100 DEF 14A 1 ddef14a.txt DEFINITIVE NOTICE & PROXY STATEMENT