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 A304367 #14 Feb 16 2025 08:33:54
%S A304367 19,28,29,37,38,39,46,47,48,49,55,56,57,58,59,64,65,66,67,68,69,73,74,
%T A304367 75,76,77,78,79,82,83,84,85,86,87,88,89,91,92,93,94,95,96,97,98,99,
%U A304367 109,118,119,127,128,129,136,137,138,139,145,146,147,148,149,154
%N A304367 Numbers n with additive persistence = 2.
%C A304367 First deviation from A298638 is at a(161); a(161) = 299, A298638(161) = 307.
%H A304367 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/AdditivePersistence.html">Additive Persistence.</a>
%F A304367 A031286(a(n)) = 2.
%e A304367 Repeatedly taking the sum of digits starting with 19 gives 10 and then 1. There are two steps, so the additive persistence is 2, and 19 is a member. - _Michael B. Porter_, May 16 2018
%t A304367 Select[Range@ 160, Length@ FixedPointList[Total@ IntegerDigits@ # &, #] == 4 &] (* _Michael De Vlieger_, May 14 2018 *)
%o A304367 (PARI) nb(n) = {my(nba = 0); while (n > 9, n = sumdigits(n); nba++); nba;}
%o A304367 isok(n) = nb(n) == 2; \\ _Michel Marcus_, May 13 2018
%Y A304367 Cf. A031286.
%Y A304367 Cf. Numbers with additive persistence k: A304366 (k=1), A304368 (k=3), A304373 (k=4).
%K A304367 nonn,base
%O A304367 1,1
%A A304367 _Jaroslav Krizek_, May 11 2018