A107692 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A107692

Primes whose product of digits is 6.

23, 61, 1123, 1213, 1231, 1321, 2113, 2131, 2311, 3121, 11161, 11213, 11321, 12113, 13121, 16111, 31121, 111611, 611111, 1111213, 1112113, 1112131, 1131121, 1211311, 2111311, 3112111, 11111161, 11112113, 11211131, 11231111, 11312111

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Michael S. Branicky, Table of n, a(n) for n = 1..10199 (all terms with <= 136 digits; terms 1..1000 from Harvey P. Dale)

MATHEMATICA

Union[ Flatten[ Table[ Select[ Sort[ FromDigits /@ Join[ Permutations[ Flatten[{6, Table[1, {n}]}]], Permutations[ Flatten[{2, 3, Table[ 1, {n - 1}]}] ]]], PrimeQ[ # ] &], {n, 0, 7}]]]

Select[Prime[Range[750000]], Times@@IntegerDigits[#]==6&] (* Harvey P. Dale, May 29 2016 *)

PROG

(Python)

from sympy import prod, isprime

from sympy.utilities.iterables import multiset_permutations

def agen(maxdigits):

for digs in range(1, maxdigits+1):

for mp in multiset_permutations("1"*(digs-1) + "236", digs):

if prod(map(int, mp)) == 6:

t = int("".join(mp))

if isprime(t): yield t

print(list(agen(8))) # Michael S. Branicky, Jun 16 2021