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A047903 a(1) = 13; for n > 0, a(n+1) = a(n) * sum of digits of a(n). 2
13, 52, 364, 4732, 75712, 1665664, 56632576, 2265303040, 56632576000, 2265303040000, 56632576000000, 2265303040000000, 56632576000000000, 2265303040000000000, 56632576000000000000, 2265303040000000000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

After the 7th element, every second element has the same beginning. a(9+2k) = 40 * a(8+2k) = 40 * 25 * a(7+2k).

LINKS

Table of n, a(n) for n=1..16.

MAPLE

P:=proc(n) local a, i, k, w; a:=13; print(a); for i from 1 by 1 to n do w:=0; k:=a; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; a:=a*w; print(a); od; end: P(1000); # Paolo P. Lava, Apr 27 2007

MATHEMATICA

NestList[# Total[IntegerDigits[#]]&, 13, 20] (* Harvey P. Dale, Jan 08 2019 *)

CROSSREFS

Cf. A047892.

Sequence in context: A022673 A152742 A213837 * A197790 A317467 A076163

Adjacent sequences:  A047900 A047901 A047902 * A047904 A047905 A047906

KEYWORD

easy,nonn,base

AUTHOR

Miklos SZABO (mike(AT)ludens.elte.hu)

STATUS

approved

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Last modified June 20 04:43 EDT 2021. Contains 345157 sequences. (Running on oeis4.)