A328581 - OEIS

A328581

Product of nonzero digits in primorial base expansion of n.

1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 4, 4, 3, 3, 3, 3, 6, 6, 4, 4, 4, 4, 8, 8, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 4, 4, 3, 3, 3, 3, 6, 6, 4, 4, 4, 4, 8, 8, 2, 2, 2, 2, 4, 4, 2, 2, 2, 2, 4, 4, 4, 4, 4, 4, 8, 8, 6, 6, 6, 6, 12, 12, 8, 8, 8, 8, 16, 16, 3, 3, 3, 3, 6, 6, 3, 3, 3, 3, 6, 6, 6, 6, 6, 6

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OFFSET

0,5

COMMENTS

a(0) = 1 as an empty product.

LINKS

Antti Karttunen, Table of n, a(n) for n = 0..32768

Index entries for sequences related to primorial base.

FORMULA

a(n) = A005361(A276086(n)).

MATHEMATICA

a[n_] := Module[{k = n, p = 2, s = 1, r}, While[{k, r} = QuotientRemainder[k, p]; k != 0 || r != 0, If[r > 0, s *= r]; p = NextPrime[p]]; s]; Array[a, 100, 0] (* Amiram Eldar, Mar 06 2024 *)

PROG

(PARI) A328581(n) = { my(m=1, p=2); while(n, if(n%p, m *= (n%p)); n = n\p; p = nextprime(1+p)); (m); };

CROSSREFS

Cf. A005361, A049345, A276086, A324655, A328582.

Cf. A276156 (positions of 1's).

Cf. also A227153 (an analogous sequence).

Sequence in context: A343504 A328582 A227153 * A238643 A140193 A073741

Adjacent sequences: A328578 A328579 A328580 * A328582 A328583 A328584

KEYWORD

nonn,base

AUTHOR

Antti Karttunen, Oct 21 2019

STATUS

approved