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 A220294 #31 Sep 08 2022 08:46:04
%S A220294 3,13,241,65281,4294901761,18446744069414584321,
%T A220294 340282366920938463444927863358058659841,
%U A220294 115792089237316195423570985008687907852929702298719625575994209400481361428481
%N A220294 a(n) = 1 - 2^(2^n) + 2^(2^(n+1)).
%C A220294 An infinite coprime sequence defined by recursion.
%F A220294 A220161(n+1) = a(n) * A220161(n).
%F A220294 a(n+1) = 1 + (a(n) - 1) * (A220161(n) - 1).
%F A220294 a(n) = A002716(2*n) = 1 + A087046(n+2) = 1 + A111403(n).
%F A220294 a(n) = A002061(A001146(n)). - _Pontus von Brömssen_, Aug 31 2021
%t A220294 Table[4^(2^m) - 2^(2^m) + 1, {m, 0, 7}] (* _Michael De Vlieger_, Aug 02 2016 *)
%o A220294 (PARI) {a(n) = if( n<0, 0, 1 - 2^(2^n) + 2^(2^(n+1)))};
%o A220294 (Maxima) A220294(n):=1 - 2^(2^n) + 2^(2^(n+1))$ makelist(A220294(n),n,0,10); /* _Martin Ettl_, Dec 10 2012 */
%o A220294 (Magma) [1 - 2^(2^n) + 2^(2^(n+1)): n in [0..10]]; // _G. C. Greubel_, Aug 10 2018
%Y A220294 Cf. A001146, A002061, A002716, A087046, A111403, A220161, A255770, A255771, A255772.
%K A220294 nonn
%O A220294 0,1
%A A220294 _Michael Somos_, Dec 10 2012