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 A344515 #5 May 22 2021 04:28:20 %S A344515 29,43,47,53,71,73,79,179,193,211,257,277,283,311,331,349,353,389,409, %T A344515 443,467,499,563,577,599,613,631,643,647,683,709,751,769,829,919,941, %U A344515 1039,1103,1117,1123,1171,1193 %N A344515 Primes p such that 2^p-1 has exactly 3 distinct prime factors. %C A344515 The corresponding Mersenne numbers are in A135977. %C A344515 a(43) >= 1237. %C A344515 The following primes are also terms of this sequence: 1301, 1303, 1327, 1459, 1531, 1559, 1907, 2311, 2383, 2887, 3041, 3547, 3833, 4127, 4507, 4871, 6883, 7673, 8233. %F A344515 2^a(n) - 1 = A135977(n). %e A344515 29 is a term since 2^29-1 = 536870911 = 233 * 1103 * 2089 has exactly 3 distinct prime factors. %t A344515 Select[Range[200], PrimeQ[#] && PrimeNu[2^# - 1] == 3 &] %Y A344515 Subsequence of A054723. %Y A344515 Cf. A000225, A065341, A135975, A135976, A135977, A135978. %K A344515 nonn,more %O A344515 1,1 %A A344515 _Amiram Eldar_, May 21 2021