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 A037131 #13 Jul 08 2025 22:02:24
%S A037131 0,1,6,28,120,497,2016,8140,32640,130813,523776,2096133,8386580,
%T A037131 33550335,134209524,536854528,2147450887,8589869054,34359607310,
%U A037131 137438691321,549755289604,2199022206975,8796090925052,35184367894531,140737479966709,562949936644106
%N A037131 a(n) = (nextprime(4^n) - nextprime(2^n))/2.
%F A037131 a(n) = A037130(n) / 2. - _Sean A. Irvine_, Dec 09 2020
%t A037131 Table[(NextPrime[4^n]-NextPrime[2^n])/2,{n,0,30}] (* _Harvey P. Dale_, May 26 2011 *)
%K A037131 nonn
%O A037131 0,3
%A A037131 _N. J. A. Sloane_
%E A037131 More terms from _Sean A. Irvine_, Dec 09 2020