login

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”).

A350676
Primes p such that p^2 + 2*p + 4 is prime.
1
3, 7, 13, 37, 61, 73, 139, 157, 229, 241, 349, 367, 397, 433, 439, 457, 523, 541, 601, 619, 709, 727, 751, 769, 787, 859, 919, 1069, 1129, 1153, 1237, 1381, 1459, 1609, 1627, 1699, 1783, 1801, 2029, 2221, 2239, 2347, 2467, 2557, 2659, 2719, 2767, 3001, 3019, 3253, 3331, 3391, 3547, 3673, 3691
OFFSET
1,1
LINKS
EXAMPLE
a(3) = 13 is a term because 13 and 13^2 + 2*13 + 4 = 199 are prime.
MAPLE
select(p -> isprime(p^2+2*p+4), [seq(ithprime(i), i=1..1000)]);
PROG
(Python)
from sympy import isprime
for p in range (2, 3700):
if isprime(p) and isprime(p**2 + 2*p + 4):
print (p, end=", ") # Karl-Heinz Hofmann, Jan 11 2022
CROSSREFS
Sequence in context: A106057 A049492 A166283 * A186721 A177945 A147448
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Jan 10 2022
STATUS
approved