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A122481 a(n) = if n < 10 then n else a(digitsum(n)) + digitsum(n), where digitsum(n)=A007953(n), the sum of digits in decimal representation of n. 1

%I

%S 0,1,2,3,4,5,6,7,8,9,2,4,6,8,10,12,14,16,18,12,4,6,8,10,12,14,16,18,

%T 12,15,6,8,10,12,14,16,18,12,15,18,8,10,12,14,16,18,12,15,18,21,10,12,

%U 14,16,18,12,15,18,21,24,12,14,16,18,12,15,18,21,24,27,14,16,18,12,15,18

%N a(n) = if n < 10 then n else a(digitsum(n)) + digitsum(n), where digitsum(n)=A007953(n), the sum of digits in decimal representation of n.

%H R. Zumkeller, <a href="/A122481/b122481.txt">Table of n, a(n) for n = 0..10000</a>

%e a(49)=a(4+9)+(4+9)=a(13)+13=a(1+3)+(1+3)+13=a(4)+4+13=4+4+13=21.

%p ds := proc(n) local t1,t2; t1 := n; t2 := 0; while t1 <> 0 do t2 := t2 + (t1 mod 10); t1 := floor(t1/10); od: t2; end;

%p M:=10000; a:=array(0..M); for n from 0 to 9 do a[n]:=n; lprint(n, a[n]); od: for n from 10 to M do a[n]:=a[ds(n)]+ds(n); lprint(n, a[n]); od:

%Y Cf. A010888.

%K nonn,base

%O 0,3

%A _Reinhard Zumkeller_, Sep 15 2006

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Last modified September 28 21:22 EDT 2021. Contains 347717 sequences. (Running on oeis4.)