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A304367 Numbers n with additive persistence = 2. 5

%I

%S 19,28,29,37,38,39,46,47,48,49,55,56,57,58,59,64,65,66,67,68,69,73,74,

%T 75,76,77,78,79,82,83,84,85,86,87,88,89,91,92,93,94,95,96,97,98,99,

%U 109,118,119,127,128,129,136,137,138,139,145,146,147,148,149,154

%N Numbers n with additive persistence = 2.

%C First deviation from A298638 is at a(161); a(161) = 299, A298638(161) = 307.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/AdditivePersistence.html">Additive Persistence.</a>

%F A031286(a(n)) = 2.

%e 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 Select[Range@ 160, Length@ FixedPointList[Total@ IntegerDigits@ # &, #] == 4 &] (* _Michael De Vlieger_, May 14 2018 *)

%o (PARI) nb(n) = {my(nba = 0); while (n > 9, n = sumdigits(n); nba++); nba;}

%o isok(n) = nb(n) == 2; \\ _Michel Marcus_, May 13 2018

%Y Cf. A031286.

%Y Cf. Numbers with additive persistence k: A304366 (k=1), A304368 (k=3), A304373 (k=4).

%K nonn,base

%O 1,1

%A _Jaroslav Krizek_, May 11 2018

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Last modified October 14 01:36 EDT 2019. Contains 327994 sequences. (Running on oeis4.)