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 A330825 #27 Dec 10 2022 02:06:20
%S A330825 6,20,272,65792,4295032832
%N A330825 Numbers of the form 2^(2^k)*F_k, where F_k is a Fermat prime, A019434.
%C A330825 Also numbers with power-spectral basis {F_n,(F_n-1)^2}. The first element of the power-spectral basis of a(n) is A019434, and the second element is A001146.
%F A330825 a(n) = A001146(n-1)*A019434(n), n = 1..5. [Corrected by _Georg Fischer_, Dec 09 2022]
%e A330825 a(2) = 2^2*(2^2+1) = 20, and the spectral basis of 20 is {5,16}, consisting of primes and powers.
%p A330825 F := n -> 2^(2^n)+1;
%p A330825 a := proc(n) if isprime(F(n)) then return 2^(2^n)*F(n) fi; end;
%p A330825 [seq(a(n),n=0..4)];
%Y A330825 Cf. A000215, A001146, A019434.
%K A330825 nonn
%O A330825 1,1
%A A330825 _Walter Kehowski_, Jan 06 2020