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A338803
Product of the nonzero digits of (n written in base 5).
1
1, 1, 2, 3, 4, 1, 1, 2, 3, 4, 2, 2, 4, 6, 8, 3, 3, 6, 9, 12, 4, 4, 8, 12, 16, 1, 1, 2, 3, 4, 1, 1, 2, 3, 4, 2, 2, 4, 6, 8, 3, 3, 6, 9, 12, 4, 4, 8, 12, 16, 2, 2, 4, 6, 8, 2, 2, 4, 6, 8, 4, 4, 8, 12, 16, 6, 6, 12, 18, 24, 8, 8, 16, 24, 32, 3, 3, 6, 9, 12, 3
OFFSET
0,3
FORMULA
G.f. A(x) satisfies: A(x) = (1 + x + 2*x^2 + 3*x^3 + 4*x^4) * A(x^5).
MATHEMATICA
Table[Times @@ DeleteCases[IntegerDigits[n, 5], 0], {n, 0, 80}]
nmax = 80; A[_] = 1; Do[A[x_] = (1 + x + 2 x^2 + 3 x^3 + 4 x^4) A[x^5] + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
PROG
(PARI) a(n) = vecprod(select(x->x, digits(n, 5))); \\ Michel Marcus, Nov 12 2020
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Ilya Gutkovskiy, Nov 12 2020
STATUS
approved