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 A031290 #11 Jul 13 2013 12:01:55 %S A031290 3,17,37,50,52,54,56,57,58,60,62,64,66,68,77,97,117,137,157,177,201, %T A031290 231,261,281,284,287,290,291,293,296,299,302,305,308,321,351,381,411, %U A031290 441,471,501,531,561,581,584,587,590,591,593,596 %N A031290 Position of n-th 3 in A007376. %C A031290 A007376(a(n)) = 3. %H A031290 Reinhard Zumkeller, <a href="/A031290/b031290.txt">Table of n, a(n) for n = 1..10000</a> %o A031290 (Haskell) %o A031290 import Data.List (elemIndices) %o A031290 a031290 n = a031290_list !! (n-1) %o A031290 a031290_list = map (+ 1) $ elemIndices 3 a007376_list %o A031290 -- _Reinhard Zumkeller_, Jul 28 2011 %Y A031290 Cf. A193428; A031287, A031288, A031289, A031291, A031292, A031293, A031294, A031295, A031296. %K A031290 nonn,less,base %O A031290 1,1 %A A031290 _Clark Kimberling_