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A338881
Product of the nonzero digits of (n written in base 8).
1
1, 1, 2, 3, 4, 5, 6, 7, 1, 1, 2, 3, 4, 5, 6, 7, 2, 2, 4, 6, 8, 10, 12, 14, 3, 3, 6, 9, 12, 15, 18, 21, 4, 4, 8, 12, 16, 20, 24, 28, 5, 5, 10, 15, 20, 25, 30, 35, 6, 6, 12, 18, 24, 30, 36, 42, 7, 7, 14, 21, 28, 35, 42, 49, 1, 1, 2, 3, 4, 5, 6, 7, 1, 1, 2, 3, 4, 5, 6, 7, 2
OFFSET
0,3
FORMULA
G.f. A(x) satisfies: A(x) = (1 + x + 2*x^2 + 3*x^3 + 4*x^4 + 5*x^5 + 6*x^6 + 7*x^7) * A(x^8).
MATHEMATICA
Table[Times @@ DeleteCases[IntegerDigits[n, 8], 0], {n, 0, 80}]
nmax = 80; A[_] = 1; Do[A[x_] = (1 + x + 2 x^2 + 3 x^3 + 4 x^4 + 5 x^5 + 6 x^6 + 7 x^7) A[x^8] + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
PROG
(PARI) a(n) = vecprod(select(x->x, digits(n, 8))); \\ Michel Marcus, Nov 14 2020
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Ilya Gutkovskiy, Nov 13 2020
STATUS
approved