A371834 Primes consisting of exactly three 3's, five 5's and seven 7's.

333555577577777, 333555577777577, 333555757775777, 333555775757777, 333555775777577, 333557555777777, 333557575777757, 333557757577757, 333557757755777, 333557775777557, 333557777555777, 333557777557757, 333557777575577, 333575577577757, 333575577757757, 333575577775577, 333575755777577

Offset

1,1

Comments

The last term is a(29943) = 777777735555533.

Links

Robert Israel, Table of n, a(n) for n = 1..29943

Example

a(3) = 333555757775777 is a term because its 15 digits consist of three 3's, five 5's and seven 7's.

Maple

select(isprime, map(t -> add(t[i]*10^(15-i), i=1..15),  combinat:-permute([3$3, 5$5, 7$7])));

Prog

(Python)
from sympy import isprime
from sympy.utilities.iterables import multiset_permutations
def agen(): # generator of terms
    for mp in multiset_permutations("333555557777777"):
        if mp[-1] != "5":
            t = int("".join(mp))
            if isprime(t):
                yield t
afull = [p for p in agen()] # Michael S. Branicky, Apr 07 2024

Crossrefs

Sequence in context: A204350 A172592 A082589 * A375012 A239922 A011528

Adjacent sequences: A371831 A371832 A371833 * A371835 A371836 A371837

Keyword

nonn,base,fini,full

Author

Zak Seidov and Robert Israel, Apr 07 2024

Status

approved