A356498 - OEIS

%I #17 Sep 11 2022 16:50:44

%S 2,3,23,41,83,101,107,113,137,179,233,239,251,281,293,353,359,401,419,

%T 479,503,557,563,569,587,683,701,743,809,839,857,863,941,953,977,1049,

%U 1091,1103,1193,1217,1277,1283,1361,1367,1427,1487,1499,1523,1607,1619,1847,1871,1877,1889,1907,1949,1973

%N Primes p such that 100*p + 11 is also prime.

%C 100*p + 11 has the effect of appending 11 to p.

%C Primes of the form 3*k + 1 are never in this sequence, as 100*(3*k + 1) + 11 can be simplified to 3*(100*k + 37).

%e 2 is a term, as 100*2 + 11 is 211, which are both prime.

%e 101 is a term, as 100*101 + 11 is 10111 which are both prime.

%o (Python)

%o from sympy import isprime

%o print([k for k in range(2000) if isprime(100*k+11) and isprime(k)])

%Y Cf. A000040, A002476 (primes of the form 3*k+1).

%Y Similar to A023237.

%K nonn

%O 1,1

%A _Daniel Blam_, Aug 09 2022