cp's OEIS Frontend

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.

%I A072545 #17 Jan 28 2023 12:09:43
%S A072545 1,2,10,11,26,35,36,50,56,86,92,101,116,122,126,134,146,156,170,176,
%T A072545 188,196,206,218,236,248,254,260,266,290,296,302,310,311,320,326,336,
%U A072545 344,356,362,376,386,392,396,404,416,426,446,452,470,476,482,486,494
%N 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.
%C A072545 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
%H A072545 D. W. Wilson, <a href="/A072545/b072545.txt">Table of n, a(n) for n = 0..10000</a>
%e A072545 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.
%o A072545 (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,",")))
%Y A072545 Cf. A025043, A025044, A068638, A084834, A254337.
%K A072545 nonn
%O A072545 0,2
%A A072545 _Amarnath Murthy_, Aug 04 2002
%E A072545 Edited and extended by _Klaus Brockhaus_, Aug 09 2002