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 A237816 #27 Jul 30 2024 07:30:23 %S A237816 2,4,6,10,70,82,143,150,220,413,426,816,5497,6649,7429,7728,7891,8248, %T A237816 14567,15522,17935,24942,37415,123773 %N A237816 k such that either 2^k + k - 3 or 2^k + k - 2 is prime. %C A237816 Numbers of this form can be represented in the numeral system described in A235860 with k - 1 ones followed to the right by k - 1 twos or k ones followed to the right by k - 1 twos, like this: 1, 12, 112, 1122, 11122, 111222, 1111222, ... (1, 3, 4, 8, 9, 17, 18, ... in decimal) and are the least numbers that need one more digit to be represented than any of their predecessors. %C A237816 The corresponding sequence of primes starts 3, 17, 67, 1031, 1180591620717411303491, ... %t A237816 fQ[n_] := PrimeQ[2^n + n - If[ OddQ@ n, 2, 3]]; Select[ Range@ 30000, fQ] %o A237816 (PARI) isok(n) = isprime(2^n + n - 3) || isprime(2^n + n - 2); \\ _Michel Marcus_, Feb 13 2014 %Y A237816 Cf. A235860, A236547. %K A237816 nonn,more %O A237816 1,1 %A A237816 _Robin Garcia_, Feb 13 2014 %E A237816 a(21)-a(22) from _Robert G. Wilson v_, Mar 03 2014 %E A237816 a(23) from _Michael S. Branicky_, May 01 2023 %E A237816 a(24) from _Michael S. Branicky_, Jul 30 2024