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A086358 Digital root of n!. 3
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 (list; graph; refs; listen; history; text; internal format)
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!) = fixed-point 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, A086353-A086361, 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

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Last modified January 27 10:15 EST 2023. Contains 359838 sequences. (Running on oeis4.)