A072545 a(0) = 1, a(n) for n > 0 is the smallest number > a(n-1) such that a(n)-a(k) is nonprime for 0 <= k < n.

1, 2, 10, 11, 26, 35, 36, 50, 56, 86, 92, 101, 116, 122, 126, 134, 146, 156, 170, 176, 188, 196, 206, 218, 236, 248, 254, 260, 266, 290, 296, 302, 310, 311, 320, 326, 336, 344, 356, 362, 376, 386, 392, 396, 404, 416, 426, 446, 452, 470, 476, 482, 486, 494

Offset

0,2

Comments

a(0) = 1, a(3) = 11, a(5) = 35, a(11) = 101 and a(33) = 311 are the only odd elements <= 10^6 and probably the only ones. If so, then for n >= 34, a(n) is the smallest even k >= a(n-1)+4 for which none of k-1, k-11, k-35, k-101 or k-311 is prime. - David W. Wilson, Dec 14 2006

Links

D. W. Wilson, Table of n, a(n) for n = 0..10000

Example

26 is the smallest number > 11 which differs from 1, 2, 10, 11 by a nonprime (25, 24, 16, 15), so 26 is the next term after 11.

Prog

(PARI) print1(a=1, ", "); v=[1]; n=1; while(n<55, a++; k=1; while(k<=n&&!isprime(a-v[k]), k++); if(k>n, n++; v=concat(v, a); print1(a, ", ")))

Crossrefs

Cf. A025043, A025044, A068638, A084834, A254337.

Sequence in context: A174569 A179884 A174570 * A023151 A342535 A265747

Adjacent sequences: A072542 A072543 A072544 * A072546 A072547 A072548

Keyword

nonn

Author

Amarnath Murthy, Aug 04 2002

Extensions

Edited and extended by Klaus Brockhaus, Aug 09 2002

Status

approved