A178553 Primes with exactly four 4's.

44449, 404449, 440441, 440443, 441443, 441449, 442447, 444043, 444047, 444341, 444343, 444347, 444349, 444401, 444403, 444421, 444461, 444463, 444469, 444473, 444487, 444547, 444641, 444649, 444841, 445447, 446441, 446447, 447443, 447449, 449441

Offset: 1

Author

Lekraj Beedassy, May 29 2010

Keywords

• nonn
• base

Links

• Daniel Starodubtsev, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A038618, A178550, A178551, A178552, A178554, A178555, A178556, A178557, A178558.

Programs

PARI

isok(p) = isprime(p) && (#select(x->(x==4), digits(p)) == 4); \\ Michel Marcus, Mar 15 2020

Extensions

Missing a(13) = 444349 inserted by Daniel Starodubtsev, Mar 15 2020