This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A133830 #9 Sep 30 2024 09:15:09
%S A133830 1,1,1,2,1,1,0,3,3,2,1,4,5,1,1,11,1,6,5,4,7,3,9,0,17,15,1,15,1,6,0,4,
%T A133830 9,14,13,3,11,25,0,6,7,0,17,7,15,2,0,30,23,6,21,2,33,1,0,3,0,14,5,6,
%U A133830 21,19,0,30,3,1,5,34,19,26,17,19,17,5,33,15,23,27,33,4,3,26,1,39,35,19,9,18
%N A133830 Least positive number k < n such that the binary trinomial 1 + 2^n + 2^k is prime, or 0 if there is no such k.
%C A133830 Sequence A081504 gives the n such that a(n) = 0. For those n, A133831(n) gives the least k > n for which the binary trinomial is prime.
%H A133830 T. D. Noe, <a href="/A133830/b133830.txt">Table of n, a(n) for n=2..2000</a>
%t A133830 Table[s=1+2^n; k=1; While[k<n && !PrimeQ[s+2^k], k++ ]; If[k==n, 0, k], {n,100}]
%Y A133830 Cf. A057732, A059242, A057196, A057200, A081091 (various forms of prime binary trinomials).
%Y A133830 Cf. A095056, A133831, A133832 (k > n equivalent).
%K A133830 nonn
%O A133830 2,4
%A A133830 _T. D. Noe_, Sep 26 2007
%E A133830 Edited by _Peter Munn_, Sep 30 2024