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A328581
Product of nonzero digits in primorial base expansion of n.
4
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
OFFSET
0,5
COMMENTS
a(0) = 1 as an empty product.
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. A276156 (positions of 1's).
Cf. also A227153 (an analogous sequence).
Sequence in context: A343504 A328582 A227153 * A238643 A140193 A073741
KEYWORD
nonn,base
AUTHOR
Antti Karttunen, Oct 21 2019
STATUS
approved