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 A257120 #25 May 03 2015 13:47:21 %S A257120 1,4,3,5,7,11,29,13,10,15,122,19,200,31,24,18,299,22,824,16,33,124, %T A257120 945,41,26,202,21,37,3093,45,7059,40,126,301,53,66,13527,826,204,42, %U A257120 28658,36,40810,130,57,947,46657,64,80,44,303,208,57449,49,133,38,828 %N A257120 Position of first occurrence of n in A256918. %C A257120 A256918(a(n)) = n and A256918(m) != n for m < a(n); %C A257120 GCD(A257218(a(n)),A257218(a(n)+1)) = n; %C A257120 if A257218 is a permutation, then also this sequence is a permutation; %C A257120 a(n) < A257475(n); a(n) = A257475(n) - A257478(n). %C A257120 a(n) >= A257122(n)-1. - _Ivan Neretin_, May 02 2015 %H A257120 Hiroaki Yamanouchi, <a href="/A257120/b257120.txt">Table of n, a(n) for n = 1..72</a> %e A257120 See A257478. %o A257120 (Haskell) %o A257120 import Data.List (elemIndex); import Data.Maybe (fromJust) %o A257120 a257120 = (+ 1) . fromJust . (`elemIndex` a256918_list) %Y A257120 Cf. A256918, A257475, A257478, A257218. %K A257120 nonn %O A257120 1,2 %A A257120 _Reinhard Zumkeller_, Apr 25 2015 %E A257120 a(41)-a(57) from _Hiroaki Yamanouchi_, May 03 2015