This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A371980 #9 May 11 2024 18:34:24 %S A371980 3,23,29,53,83,113,131,173,191,233,239,251,281,293,419,431,443,491, %T A371980 593,641,653,659,683,743,761,809,911,953,1013,1049,1103,1223,1289, %U A371980 1439,1499,1559,1583,1601,1733,1973,2003,2039,2063,2069,2129,2141,2273,2339,2351,2393,2399,2543,2549,2693,2741,2753 %N A371980 Sophie Germain primes p such that 4*p + 3 is a composite number. %e A371980 a(1) = 3 is prime and 2*3 + 1 = 7 also but not 4*3 + 3 = 15. %t A371980 Select[Prime[Range[410]], And[PrimeQ[2 # + 1], CompositeQ[4 # + 3]] &] (* _Michael De Vlieger_, Apr 19 2024 *) %o A371980 (Python) %o A371980 import sympy as sp %o A371980 l = [] %o A371980 for i in range(2,2800): %o A371980 if sp.isprime(i) and sp.isprime(2*i + 1) and not(sp.isprime(4*i + 3)): %o A371980 l.append(i) %o A371980 print(l) %Y A371980 Cf. A005384. %K A371980 nonn %O A371980 1,1 %A A371980 _Alexandre Herrera_, Apr 15 2024