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.

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, 12, 15, 6, 8, 10, 12, 14, 16, 18, 12, 15, 18, 8, 10, 12, 14, 16, 18, 12, 15, 18, 21, 10, 12, 14, 16, 18, 12, 15, 18, 21, 24, 12, 14, 16, 18, 12, 15, 18, 21, 24, 27, 14, 16, 18, 12, 15, 18

Offset

0,3

Links

R. Zumkeller, Table of n, a(n) for n = 0..10000

Example

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

Maple

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;
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:

Mathematica

lim=75; Do[a[n]=n, {n, 0, 9}]; Do[a[n]=a[Total[IntegerDigits[n]]]+Total[IntegerDigits[n]], {n, 10, lim}]; Table[a[n], {n, 0, lim}] (* James C. McMahon, Oct 27 2024 *)

Crossrefs

Cf. A007953, A010888.

Sequence in context: A049105 A125959 A043269 * A110805 A356234 A284255

Adjacent sequences: A122478 A122479 A122480 * A122482 A122483 A122484

Keyword

nonn,base

Author

Reinhard Zumkeller, Sep 15 2006

Status

approved