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 A031291 #11 Jul 13 2013 12:01:55 %S A031291 4,19,39,59,70,72,74,76,78,79,80,82,84,86,88,99,119,139,159,179,204, %T A031291 234,264,294,311,314,317,320,323,324,326,329,332,335,338,354,384,414, %U A031291 444,474,504,534,564,594,611,614,617,620,623,624 %N A031291 Position of n-th 4 in A007376. %C A031291 A007376(a(n)) = 4. %H A031291 Reinhard Zumkeller, <a href="/A031291/b031291.txt">Table of n, a(n) for n = 1..10000</a> %o A031291 (Haskell) %o A031291 import Data.List (elemIndices) %o A031291 a031291 n = a031291_list !! (n-1) %o A031291 a031291_list = map (+ 1) $ elemIndices 4 a007376_list %o A031291 -- _Reinhard Zumkeller_, Jul 28 2011 %Y A031291 Cf. A193428; A031287, A031288, A031289, A031290, A031292, A031293, A031294, A031295, A031296. %K A031291 nonn,less,base %O A031291 1,1 %A A031291 _Clark Kimberling_