
1, 1, 2, 6, 6, 3, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9
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OFFSET

0,3


COMMENTS

a(n) = 9 for n >= 6.


LINKS

Table of n, a(n) for n=0..105.
Index entries for linear recurrences with constant coefficients, signature (1).


FORMULA

a(n) = A010888(n!) = fixedpoint of A007953(n!). It equals n! modulo(9); at r = 0 use 9.
G.f.: (1 + x^2 + 4*x^3  3*x^5 + 6*x^6)/(1  x).  Stefano Spezia, Jan 26 2023


EXAMPLE

n = 5, 5 != 120, iteration list = {120,3}, a(5) = 3.


MATHEMATICA

sud[x_] := Apply[Plus, DeleteCases[IntegerDigits[x], 0]]; Table[FixedPoint[sud, w!], {w, 1, 87}]


CROSSREFS

Cf. A000142, A086353A086361, A007953, A010888, A038194, A029898, A004152.
Sequence in context: A153845 A105815 A136696 * A004152 A071678 A316164
Adjacent sequences: A086355 A086356 A086357 * A086359 A086360 A086361


KEYWORD

nonn,base,easy,changed


AUTHOR

Labos Elemer, Jul 21 2003


EXTENSIONS

a(0) = 1 prepended by Alois P. Heinz, Dec 05 2018


STATUS

approved

