

A072545


a(0) = 1, a(n) for n > 0 is the smallest number > a(n1) such that a(n)a(k) is nonprime for 0 <= k < n.


3



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
(list;
graph;
refs;
listen;
history;
text;
internal format)



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(n1)+4 for which none of k1, k11, k35, k101 or k311 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(av[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 A265747 A104459
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



