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 A076131 #14 Oct 17 2023 17:04:08
%S A076131 0,1,5,41,657,21025,1345601,172236929,44092653825,22575438758401,
%T A076131 23117249288602625,47344126543058176001,193921542320366288900097,
%U A076131 1588605274688440638669594625,26027708820495411423962638336001,852875962629993641540407732994080769
%N A076131 a(n) = 2^n*a(n-1) + 1, a(0) = 0.
%C A076131 Base-2 expansion is same as base 10 expansion of A076127.
%H A076131 Vincenzo Librandi, <a href="/A076131/b076131.txt">Table of n, a(n) for n = 0..80</a>
%F A076131 a(n) = floor(c*2^((n+1)*(n+2)/2)) where c = sum(k>=1, 1/2^A000217(k))=0.6416325... - _Benoit Cloitre_, Nov 01 2002
%t A076131 a[0] = 0; a[n_] := 2^n a[n - 1] + 1; Table[ a[n], {n, 0, 13}]
%o A076131 (PARI) a(n)=if(n<0,0,subst(Polrev(Vec(sum(k=1,n,x^(k*(k+1)/2)))),x,2))
%o A076131 (PARI) a(n)=if(n<1,0,1+a(n-1)*2^n)
%Y A076131 Cf. A000217, A073587, A076127, A190405.
%K A076131 easy,nonn,base
%O A076131 0,3
%A A076131 Kyle Hunter (hunterk(AT)raytheon.com), Oct 31 2002
%E A076131 Edited and extended by _Robert G. Wilson v_, Oct 31 2002
%E A076131 Formula corrected by _Vaclav Kotesovec_, Aug 11 2012