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 A344260 #21 May 23 2021 03:06:43
%S A344260 1,3,21,585,69905,34636833,69810262081,567382630219905,
%T A344260 18519084246547628289,2422583247133816584929793,
%U A344260 1268889750375080065623288448001,2659754699919401766201267083003561985,22306191045953951743035482794815064402563073,748380193317489370459454048174977015562807531282433
%N A344260 a(n) is the number of relations from an n-element set into a set of at most n elements.
%C A344260 Symmetrically, also the number of relations from a set of at most n elements into an n-element set.
%F A344260 a(n) = (2^(n+n^2) - 1)/(2^n - 1) for n > 0 and a(0) = 1.
%F A344260 a(n) ~ 2^(n^2).
%F A344260 a(n) = A275779(n) + 1. - _Hugo Pfoertner_, May 14 2021
%t A344260 Join[{1},Table[(2^(n+n^2)-1)/(2^n-1),{n,13}]]
%Y A344260 Row sums of A344110.
%Y A344260 Cf. A000079, A002416, A031971, A089072, A117401, A275779.
%K A344260 nonn
%O A344260 0,2
%A A344260 _Stefano Spezia_, May 13 2021