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%I #10 Mar 26 2024 15:41:15
%S 1,1,2,3,4,5,6,1,1,2,3,4,5,6,2,2,4,6,8,10,12,3,3,6,9,12,15,18,4,4,8,
%T 12,16,20,24,5,5,10,15,20,25,30,6,6,12,18,24,30,36,1,1,2,3,4,5,6,1,1,
%U 2,3,4,5,6,2,2,4,6,8,10,12,3,3,6,9,12,15,18,4,4,8,12
%N Product of the nonzero digits of (n written in base 7).
%H Alois P. Heinz, <a href="/A338880/b338880.txt">Table of n, a(n) for n = 0..9603</a>
%F G.f. A(x) satisfies: A(x) = (1 + x + 2*x^2 + 3*x^3 + 4*x^4 + 5*x^5 + 6*x^6) * A(x^7).
%t Table[Times @@ DeleteCases[IntegerDigits[n, 7], 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 + 6 x^6) A[x^7] + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
%o (PARI) a(n) = vecprod(select(x->x, digits(n, 7))); \\ _Michel Marcus_, Nov 14 2020
%Y Cf. A007093, A051801, A053828, A117592, A309958.
%K nonn,base
%O 0,3
%A _Ilya Gutkovskiy_, Nov 13 2020
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