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 A376904 #9 Oct 19 2024 08:36:07 %S A376904 1,2,4,3,11,5,26,8,6,12,82,7,97,27,13,9,202,17,244,10,28,83,424,18,14, %T A376904 98,46,29,664,15,741,38,84,203,16,19,1182,245,99,39,1416,20,1584,85, %U A376904 47,425,1923,21,30,62,204,100,2463,22,86,31,246,665,3354,23,3723 %N A376904 Inverse permutation to A376903. %H A376904 Rémy Sigrist, <a href="/A376904/b376904.txt">Table of n, a(n) for n = 1..10000</a> %H A376904 Rémy Sigrist, <a href="/A376904/a376904.txt">C++ program</a> %H A376904 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %e A376904 A376903(42) = 88, so a(88) = 42. %o A376904 (C++) // See Links section. %o A376904 (Python) %o A376904 from itertools import count, islice %o A376904 def agen(): # generator of terms; uses A376903gen() in A376903 %o A376904 adict, n = dict(), 1 %o A376904 for k, v in enumerate(A376903gen(), 1): %o A376904 if v not in adict: %o A376904 adict[v] = k %o A376904 while n in adict: yield adict[n]; n += 1 %o A376904 print(list(islice(agen(), 61))) # _Michael S. Branicky_, Oct 16 2024 %Y A376904 Cf. A376903. %K A376904 nonn %O A376904 1,2 %A A376904 _Rémy Sigrist_, Oct 09 2024