OFFSET
1,1
COMMENTS
All terms of <= 32 digits have digit sum 199. - Robert Israel, Jun 25 2018
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
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.
MAPLE
S:= proc(d, t, m) # d digits of sum t with max m
option remember;
local j;
if d*m < t then return [] fi;
if d = 1 then if t > 0 then return [[t]] else return [] fi fi;
[seq(op(map(L -> [op(L), j], procname(d-1, t-j, j))), j=1..min(m, t))]
end proc:
seq(op(sort(map(t -> add(t[-i]*10^(i-1), i=1..nops(t)), S(d, 199, 9)))), d=23..24); # Robert Israel, Jun 25 2018
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Jun 25 2018
STATUS
approved