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 A260641 #7 Nov 17 2015 18:45:41 %S A260641 2,3,7,9,12,13,17,23,25,26,31,33,37,41,44,45,46,48,49,55,56,57,61,65, %T A260641 67 %N A260641 Numbers n such that 2^n-1 is in A004782 but not in A081767. %C A260641 It appears that the numbers in A004782 \ A081767 are all of the form 2^n-1; this sequence gives the corresponding n-values. %H A260641 M. Alekseyev, <a href="http://home.gwu.edu/~maxal/gpscripts/">PARI/GP Scripts for Miscellaneous Math Problems</a>, sect. III: Binomial coefficients modulo integers, binomod.gp (v.1.4, 11/2015). %o A260641 (PARI) for(k=2,999, n=2^k-1; !binomod(2*n-2, n-1, n^2-n) && binomod(2*n, n,n^2-1) && print1(k", ")) %K A260641 nonn,more %O A260641 1,1 %A A260641 _M. F. Hasler_, Nov 11 2015