A338863 - OEIS

%I #6 Nov 13 2020 14:22:39

%S 1,1,2,3,4,5,1,1,2,3,4,5,2,2,4,6,8,10,3,3,6,9,12,15,4,4,8,12,16,20,5,

%T 5,10,15,20,25,1,1,2,3,4,5,1,1,2,3,4,5,2,2,4,6,8,10,3,3,6,9,12,15,4,4,

%U 8,12,16,20,5,5,10,15,20,25,2,2,4,6,8,10,2,2,4

%N Product of the nonzero digits of (n written in base 6).

%F G.f. A(x) satisfies: A(x) = (1 + x + 2*x^2 + 3*x^3 + 4*x^4 + 5*x^5) * A(x^6).

%t Table[Times @@ DeleteCases[IntegerDigits[n, 6], 0], {n, 0, 80}]

%t nmax = 80; A[_] = 1; Do[A[x_] = (1 + x + 2 x^2 + 3 x^3 + 4 x^4 + 5 x^5) A[x^6] + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]

%o (PARI) a(n) = vecprod(select(x->x, digits(n, 6))); \\ _Michel Marcus_, Nov 13 2020

%Y Cf. A007092, A051801, A117592, A309957.

%K nonn,base

%O 0,3

%A _Ilya Gutkovskiy_, Nov 12 2020