OFFSET
1,1
COMMENTS
Take n, then starting with k=1, apply iteration k = digitsum(n*k), stop when the new k appears before in the row, length of the n-th row is a(n):
n=1: {1,1}, a(1)=2
n=2: {1,2,4,8,7,5,1}, a(2)=7
n=3: {1,3,9,9}, a(3)=4
n=4: {1,4,7,10,4}, a(4)=5.
MATHEMATICA
Table[k = 1; s = {k}; While[k = Total[IntegerDigits[n*k]]; FreeQ[s, k], AppendTo[s, k]]; Length[s] + 1, {n, 100}]
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Zak Seidov, Oct 20 2011
STATUS
approved