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 A225609 #44 Dec 31 2016 01:07:46
%S A225609 0,1,4,33,532,17057,1092180,139816097,35794013012,18326674478241,
%T A225609 18766550459731796,38433913668205196449,157425329151518944386900,
%U A225609 1289628334843156860622681249,21129270795495611155960953970516,692363946716428521201685400328549537
%N A225609 Recurrence a(n) = 2^n*a(n-1) + a(n-2) with a(0)=0, a(1)=1.
%H A225609 Seiichi Manyama, <a href="/A225609/b225609.txt">Table of n, a(n) for n = 0..81</a>
%F A225609 a(n) ~ c * 2^(n^2/2 + n/2), where c = 0.52087674149344124670486211129137...
%t A225609 RecurrenceTable[{a[n]==2^n*a[n-1]+a[n-2],a[0]==0,a[1]==1},a,{n,0,15}]
%Y A225609 Cf. A006116, A073587, A073588, A076131, A228465, A228467.
%K A225609 nonn
%O A225609 0,3
%A A225609 _Vaclav Kotesovec_, Aug 22 2013