OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Additive Persistence
FORMULA
A031286(a(n)) = 4.
EXAMPLE
Repeatedly taking the sum of digits starting with 19999999999999999999999 gives 199, 19, 10 and 1. There are four steps, so the additive persistence is 4 and 19999999999999999999999 is a member.
MATHEMATICA
Take[ Sort@ Flatten[ (FromDigits /@ Permutations@#) & /@ IntegerPartitions[ 199, {23}, Range@ 9]], 10000] (* first 10000 terms, Giovanni Resta, May 29 2018 *)
PROG
(PARI) nb(n) = {my(nba = 0); while (n > 9, n = sumdigits(n); nba++); nba; }
isok(n) = nb(n) == 4; \\ Michel Marcus, May 29 2018
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, May 28 2018
STATUS
approved