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 A134927 #25 Jun 11 2024 07:43:34
%S A134927 1,1,6,21,81,306,1161,4401,16686,63261,239841,909306,3447441,13070241,
%T A134927 49553046,187869861,712268721,2700415746,10238053401,38815407441,
%U A134927 147160382526,557927369901,2115263257281,8019571881546,30404505416481
%N A134927 a(0)=a(1)=1; a(n) = 3*(a(n-1) + a(n-2)).
%H A134927 Joshua Zucker, Feb 23 2008, <a href="/A134927/b134927.txt">Table of n, a(n) for n = 0..50</a>
%H A134927 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,3).
%F A134927 From _R. J. Mathar_, Jan 31 2008: (Start)
%F A134927 O.g.f.: (-1+2*x)/(-1 + 3*x + 3*x^2).
%F A134927 a(n) = A030195(n+1)-2*A030195(n). (End)
%F A134927 a(n) = A108306(n-1), n>0. - _R. J. Mathar_, Oct 04 2011
%F A134927 a(n) ~ 3.7912878474...^n, where the constant is A090458. - _Charles R Greathouse IV_, Oct 04 2011
%p A134927 a[0]:=1:a[1]:=1:for n from 2 to 50 do a[n]:=3*a[n-1]+3*a[n-2] od: seq(a[n], n=0..33); # _Zerinvary Lajos_, Dec 14 2008
%t A134927 LinearRecurrence[{3, 3}, {1, 1}, 30]
%o A134927 (Sage)
%o A134927 from sage.combinat.sloane_functions import recur_gen2
%o A134927 it = recur_gen2(1,1,3,3)
%o A134927 [next(it) for i in range(25)] # _Zerinvary Lajos_, Jun 25 2008
%o A134927 (PARI) a=[1,1];for(i=2,10,a=concat(a,3*a[#a]+3*a[#a-1]));a \\ _Charles R Greathouse IV_, Oct 04 2011
%Y A134927 Essentially the same as A108306.
%K A134927 nonn,easy
%O A134927 0,3
%A A134927 _Rolf Pleisch_, Jan 29 2008
%E A134927 More terms from _Joshua Zucker_, Feb 23 2008