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 A078726 #8 Apr 11 2021 11:08:12
%S A078726 3,5,17,257,35567,2244677999,111344445566777789,
%T A078726 111222233333334444445666666777788899,
%U A078726 111111222223333333344444455555555566666666777777778888888999999999999
%N A078726 Fermat numbers 2^(2^n) + 1 with digits sorted in increasing order and zeros suppressed.
%C A078726 The 0, 1, 2, 3, 5 and 7 terms of this sequence are primes. Are there any more?
%t A078726 Table[FromDigits[Sort[IntegerDigits[2^2^n+1]]/.(0->Nothing)],{n,0,10}] (* _Harvey P. Dale_, Apr 11 2021 *)
%Y A078726 Cf. A000215.
%K A078726 base,nonn,nice
%O A078726 0,1
%A A078726 _Jason Earls_, Dec 20 2002