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 A112648 #12 Jan 21 2019 19:01:55 %S A112648 2,4,7,8,11,12,14,15,16,20,28,29,31,32,34,40,41,42,45 %N A112648 Integers k for which the k-th Mersenne prime exponent is a Gaussian prime (3 mod 4). %e A112648 A000043(45) = 37156667 is congruent to 3 mod 4, so 45 is in this sequence. %e A112648 A000043(46) = 42643801 is congruent to 1 mod 4, so 46 is not in this sequence. %t A112648 Select[Range@ 45, Mod[MersennePrimeExponent@ #, 4] == 3 &] (* _Michael De Vlieger_, Jul 22 2018 *) %Y A112648 Cf. A000043, A112633, A112634, A112649. %K A112648 nonn %O A112648 1,1 %A A112648 _Jorge Coveiro_, Dec 27 2005 %E A112648 Edited by _Don Reble_, Jan 25 2006 %E A112648 More terms from _Gord Palameta_, Jul 21 2018