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 A277578 #7 Jun 02 2025 12:19:46 %S A277578 0,1,4,2,1750,8771,3,5,16,14,12,10,8,6,8765,25,1746,1744,23,26353,7,9, %T A277578 11,13,15,17,52,50,48,46,44,42,40,38,36,34,32,30,28,26,24,22,20,18, %U A277578 8745,77,1732,5246,75,15800,8741,73,26331,8739,71,1728,5242,69,15796 %N A277578 Left inverse of A277558. %C A277578 If A277558 is a permutation, this is the full inverse of it. %C A277578 After 10^11 terms of A277558, the smallest number which has not appeared is 609790506. The largest number in the first 600 million terms of this sequence is a(597249348) = 97840303230. %H A277578 Benjamin Chaffin, <a href="/A277578/b277578.txt">Table of n, a(n) for n = 0..10000</a> %e A277578 A277558(16) = 8, so a(8) = 16. %Y A277578 Cf. A277558, A005132 %K A277578 nonn %O A277578 0,3 %A A277578 _Benjamin Chaffin_, Oct 20 2016