A384443 a(n) is the product of the prime digits of n; or 1 if n contains no prime digits.

1, 2, 3, 1, 5, 1, 7, 1, 1, 1, 1, 2, 3, 1, 5, 1, 7, 1, 1, 2, 2, 4, 6, 2, 10, 2, 14, 2, 2, 3, 3, 6, 9, 3, 15, 3, 21, 3, 3, 1, 1, 2, 3, 1, 5, 1, 7, 1, 1, 5, 5, 10, 15, 5, 25, 5, 35, 5, 5, 1, 1, 2, 3, 1, 5, 1, 7, 1, 1, 7, 7, 14, 21, 7, 35, 7, 49, 7, 7, 1, 1, 2, 3, 1

Offset

1,2

Links

Felix Huber, Table of n, a(n) for n = 1..10000

Example

a(2025) = 2*2*5 = 20.

Maple

A384443:=n->mul(select(isprime, convert(n, 'base', 10))); seq(A384443(n), n=1..84);

Mathematica

a[n_]:=If[ContainsAny[IntegerDigits[n], {2, 3, 5, 7}], Times@@Select[IntegerDigits[n], PrimeQ], 1]; Array[a, 100] (* James C. McMahon, Jun 20 2025 *)

Prog

(PARI) a(n) = vecprod(select(isprime, digits(n))); \\ Michel Marcus, Jun 04 2025

Crossrefs

Cf. A002110, A007947, A007954, A384444, A384445, A384505.

Sequence in context: A371356 A227643 A249386 * A089026 A080305 A220137

Adjacent sequences: A384440 A384441 A384442 * A384444 A384445 A384446

Keyword

nonn,base,easy

Author

Felix Huber, Jun 03 2025

Status

approved