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 A031317 #8 Dec 26 2023 23:54:14 %S A031317 36,38,40,42,44,157,160,163,166,169,307,310,313,316,319,457,460,463, %T A031317 466,469,546,549,552,555,558,561,564,567,570,573,576,579,582,585,588, %U A031317 591,594,597,600,603,606,607,609,610,612,613,615 %N A031317 Position of n-th 4 in A031312. %t A031317 Flatten[Position[Flatten[IntegerDigits[2*Range[500]-1]],4]] (* _Harvey P. Dale_, Aug 12 2015 *) %Y A031317 Cf. A031312. %K A031317 nonn %O A031317 1,1 %A A031317 _Clark Kimberling_