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 A020498 a(n) is the least number > a(n-1) such that a(1) through a(n) do not contain all residues modulo any prime. 4
 1, 3, 7, 9, 13, 19, 21, 27, 31, 33, 37, 43, 49, 51, 57, 63, 69, 73, 79, 87, 91, 97, 99, 103, 111, 117, 121, 129, 133, 139, 141, 147, 153, 157, 159, 163, 169, 177, 183, 187, 189, 199, 201, 211, 213, 217, 231, 241, 243, 247, 253, 261, 267, 271, 273, 279, 283, 289 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Conjecturally, a(n) is the smallest number such that n primes occur infinitely often among (x+a(1), ...,x+a(n)). REFERENCES R. K. Guy's "Unsolved Problems in Number Theory" (2nd edition, Springer, 1994), Section A9. LINKS David W. Wilson, Table of n, a(n) for n = 1..10000 CROSSREFS Cf. A020497, A008407. Sequence in context: A141544 A172407 A088649 * A200567 A107771 A215800 Adjacent sequences:  A020495 A020496 A020497 * A020499 A020500 A020501 KEYWORD nonn AUTHOR EXTENSIONS More terms from David Wasserman, Aug 17 2005 Old name has been interchanged with Wasserman's comment, as old name only a conjectural definition of the sequence. Edited by Christopher J. Smyth, May 12 2016 STATUS approved

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