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 A330826 #21 Jan 12 2020 13:41:10
%S A330826 12,40,544,131584,8590065664
%N A330826 Numbers of the form 2^((2^n)+1)*F_n, where F_n is a Fermat prime, A019434.
%C A330826 Also numbers with power-spectral basis {F_n^2, (F_n-1)^2}.
%C A330826 The first factor of a(n) is 2^A000051(n). The first element of the power-spectral basis of a(n) is A001146, and the second element is A330828.
%F A330826 a(n) =2^A000051(n)*A019434(n).
%e A330826 a(2) = 2^(2+1)*5 = 40, and the spectral basis of 40 is {25,16}, consisting of primes and powers.
%p A330826 F := n -> 2^(2^n)+1;
%p A330826 a := proc(n) if isprime(F(n)) then return 2^((2^n)+1)*F(n) fi; end;
%Y A330826 Cf. A001146, A000215, A019434, A000051, A330828.
%K A330826 nonn,hard,more
%O A330826 1,1
%A A330826 _Walter Kehowski_, Jan 06 2020