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a(1)=1, a(n) = 2 + maximal digit of Sum_{j=1..n-1} a(j).
1

%I #6 Jul 08 2018 01:39:13

%S 1,3,6,3,5,10,10,10,10,10,10,10,10,11,11,4,6,5,7,6,10,10,10,10,10,11,

%T 11,4,6,5,7,6,10,10,10,10,10,11,11,5,7,5,9,8,7,8,11,10,11,6,9,8,6,6,8,

%U 6,7,9,8,9,10,11,7,7,10,10,10,10,10,10,10,10,11,11,8,10,10,10,10,10,10,10

%N a(1)=1, a(n) = 2 + maximal digit of Sum_{j=1..n-1} a(j).

%C For n > 1, 3 <= a(n) <= 11 by definition. Also subsequences with repeating terms may be arbitrarily long. What about any other patterns, periods, etc.?

%t a[1]=i=s=1;Do[i++;b=2+Max[IntegerDigits[s]];a[i]=b;s+=b,{145}]; Table[a[k],{k,i}]

%K base,nonn

%O 1,2

%A _Zak Seidov_, Oct 31 2007