A178551 Primes with exactly two 2's.

223, 227, 229, 1223, 1229, 2027, 2029, 2129, 2203, 2207, 2213, 2237, 2239, 2243, 2251, 2267, 2269, 2273, 2281, 2287, 2293, 2297, 2423, 2521, 2621, 2729, 2927, 3221, 3229, 4229, 5227, 6221, 6229, 7229, 8221, 9221, 9227, 10223, 12203, 12211, 12239, 12241, 12251, 12253

Offset: 1

Author

Lekraj Beedassy, May 29 2010

Keywords

• nonn
• base
• changed

Links

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

Crossrefs

Cf. A038618, A178550, A178552, A178553, A178554, A178555, A178556, A178557, A178558.

Programs

Mathematica

Select[Prime[Range[1500]],Count[IntegerDigits[#],2]==2 &] (* Stefano Spezia, Aug 29 2025 *)

Python

from sympy import isprime
print([i for i in range(10000) if str(i).count('2') == 2 and isprime(i)]) # Daniel Starodubtsev, Mar 29 2020