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 A057931 #4 Jul 12 2022 20:55:40 %S A057931 -1,0,-1,2,5,11,23,32,47,83,131,239,311,527,731,965,1703,2675,3827, %T A057931 6359,9659,14555,23087,33041,45995,77519,120467,177635,252713,405317, %U A057931 554033,795827,1335083,1819523,2491229,4183463,5920211,8051987,12530963,20132057 %N A057931 Positions at which powers of 2 occur in A057929. (Or -1 if it does not occur.) %Y A057931 Cf. A057929, A057930. %K A057931 easy,sign %O A057931 0,4 %A A057931 Larry Reeves (larryr(AT)acm.org), Oct 03 2000 %E A057931 More terms from _Sean A. Irvine_, Jul 12 2022