A161995 - OEIS

A161995

a(n) represents the minimum number k, not already present in the sequence, whose digit sum is equal to the digital root of Sum_{j=0..n-1} a(j), with a(0)=0 and a(1)=1.

%I #12 Nov 26 2015 09:38:04

%S 0,1,10,2,4,8,7,5,100,11,13,17,16,14,1000,20,22,26,25,23,10000,101,31,

%T 35,34,32,100000,110,40,44,43,41,1000000,200,103,53,52,50,10000000,

%U 1001,112,62,61,104,100000000,1010,121,71,70,113,1000000000,1100,130,80,106

%N a(n) represents the minimum number k, not already present in the sequence, whose digit sum is equal to the digital root of Sum_{j=0..n-1} a(j), with a(0)=0 and a(1)=1.

%C From a(3) onward the digital root is periodic with period length equal to six: 1,2,4,8,7,5.

%e a(3) = 10 because a(0) + a(1) = 1 and 10 is the minimum number greater than 1 whose digit sum is equal to 1.

%Y Cf. A010888.

%K easy,nonn,base

%O 0,3

%A _Paolo P. Lava_ & _Giorgio Balzarotti_, Jun 24 2009