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 A137674 #20 Jul 28 2023 10:36:53 %S A137674 1,2,5,13,35,84,198,414,960,1898,4263,8556,18473,37490,79526,159956, %T A137674 338873,680306,1438941,2869908,6057397,12038460,25300258,50460684, %U A137674 105275708,211424744,437486956,879869316,1810901110,3642407379,7495644753,15038540180,30957576741 %N A137674 Numbers m such that A137671(m) = 1. %H A137674 Rémy Sigrist, <a href="/A137674/a137674.txt">C program for A137674</a>. %F A137674 A137671(a(n)) = 1. %F A137674 A137672(a(n)) = 1. %F A137674 For n > 1: A137671(a(n)-1) = 2^(n-1)-1 = A000225(n-1), A137672(a(n)-1) = n-1, and a(n) = A137673(A137671(a(n)-1)) + 1. %t A137674 b[1] = 1; b[n_] := b[n] = Count[Array[s, n - 1], s[n - 1]]; s[n_] := s[n] = DigitCount[b[n], 2, 1]; Select[Range[10000], b[#] == 1 &] (* _Amiram Eldar_, Jul 27 2023 *) %o A137674 (C) See Links section. %Y A137674 Cf. A000225, A137671, A137672, A137673. %K A137674 nonn,base %O A137674 1,2 %A A137674 _Reinhard Zumkeller_, Feb 05 2008 %E A137674 More terms from _Rémy Sigrist_, Jun 28 2019