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 A073587 #32 Mar 23 2024 19:15:29
%S A073587 1,3,13,105,1681,53793,3442753,440672385,112812130561,57759810847233,
%T A073587 59146046307566593,121131102837896382465,496152997224023582576641,
%U A073587 4064485353259201188467843073,66592528027798752271857140908033,2182103958414909514444214793274425345
%N A073587 a(n) = a(n-1)*2^n + 1 where a(0)=1.
%C A073587 Also, number of nodes in an n-ary tree with increasing fanout as the level increases. - _Dhruv Matani_, Apr 12 2012
%F A073587 a(n) = floor(D*2^(n*(n+1)/2)) where D is a constant, D=1.64163256065515386629... = Sum_{k>=0} 1/2^(k(k+1)/2) = A299998. - _Benoit Cloitre_, Sep 01 2002
%t A073587 a = 1; Table[a = a*2^n + 1, {n, 14}] (* _Jayanta Basu_, Jul 02 2013 *)
%o A073587 (UBASIC)
%o A073587 25 A=1
%o A073587 30 for I=1 to 20
%o A073587 40 A=A*2^I+1
%o A073587 50 print A
%o A073587 60 next
%o A073587 70 end
%Y A073587 Cf. A000225 (nodes in a binary tree).
%Y A073587 Cf. A006125, A117261, A299998.
%K A073587 easy,nonn
%O A073587 0,2
%A A073587 _Felice Russo_, Aug 28 2002
%E A073587 Added a(0)=1. Added information from duplicate sequence A182104. - _N. J. A. Sloane_, Dec 28 2015