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 A344781 #18 May 08 2024 08:52:10 %S A344781 4,7,8,28,32,81,669,1108,1699,1839,2319,9566,14866,30855,35932,56048, %T A344781 70915,72578 %N A344781 Numbers k such that A070313(k) = 2^k - (2*k+1) is a prime number. %C A344781 The corresponding primes are 7, 113, 239, 268435399, 4294967231, 2417851639229258349412189, ... %C A344781 If k is a term of this sequence then 2^(k-1)*(2^k-(2*k+1)) is a term of A056075 (see _Farideh Firoozbakht_'s comment in A056075). %e A344781 4 is a term since 2^4 - (2*4+1) = 16 - 9 = 7 is a prime. %e A344781 7 is a term since 2^7 - (2*7+1) = 128 - 15 = 113 is a prime. %t A344781 Select[Range[2400], PrimeQ[2^# - 2*# - 1] &] %Y A344781 Cf. A056075, A070313. %K A344781 nonn,more %O A344781 1,1 %A A344781 _Amiram Eldar_, May 28 2021 %E A344781 a(16)-a(18) from _Michael S. Branicky_, May 07 2024