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A110728
Digital factorial: a(0) = 1, a(n) = n * (the sum of the digits of a(n-1)).
4
1, 1, 2, 6, 24, 30, 18, 63, 72, 81, 90, 99, 216, 117, 126, 135, 144, 153, 162, 171, 180, 189, 396, 414, 216, 225, 234, 243, 252, 261, 270, 279, 576, 594, 612, 315, 324, 333, 342, 351, 360, 369, 756, 774, 792, 810, 414, 423, 432, 441, 450, 459, 936, 954, 972
OFFSET
0,3
LINKS
EXAMPLE
a(4) = 24, a(5) = 5*(2+4) = 30, a(6) = 6*3 = 18.
MAPLE
a:= proc(n) option remember; `if`(n=0, 1,
n*add(i, i=convert(a(n-1), base, 10)))
end:
seq(a(n), n=0..60); # Alois P. Heinz, Dec 12 2020
MATHEMATICA
DigitSum[n_, 10] := Total[IntegerDigits[n, 10]]; A110728[0] := 1; A110728[n_] := A110728[n] = n*DigitSum[A110728[n - 1], 10]; Table[A110728[n], {n, 0, 50}] (* G. C. Greubel, Sep 06 2017 *)
PROG
(PARI) s=vector(1001, n, 1); for(n=2, #s, s[n]=(n-1)*sumdigits(s[n-1])); s \\ Colin Barker, Nov 20 2014
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Aug 09 2005
EXTENSIONS
a(22) and a(32) corrected, name clarified, and more terms added by Colin Barker, Nov 20 2014
STATUS
approved