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 A110211 #15 Aug 29 2025 20:37:34
%S A110211 -1,3,-15,69,-327,1545,-7311,34593,-163695,774609,-3665487,17345265,
%T A110211 -82078671,388400433,-1837930575,8697180849,-41155501647,194749924785,
%U A110211 -921566538831,4360899684273,-20635998872655,97650595130289,-462087577545807,2186621894493105
%N A110211 a(n+3) = 6*a(n) - 5*a(n+2), a(0) = -1, a(1) = 3, a(2) = -15.
%H A110211 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-5,0,6).
%F A110211 G.f.: (1+2*x)/((x-1)*(6*x^2+6*x+1)).
%F A110211 a(n) = (-3+(-3-sqrt(3))^n*(-5-2*sqrt(3))+(-3+sqrt(3))^n*(-5+2*sqrt(3)))/13. - _Harvey P. Dale_, Mar 28 2012 [corrected by _Jason Yuen_, Aug 29 2025]
%p A110211 seriestolist(series((1+2*x)/((x-1)*(6*x^2+6*x+1)), x=0,25)); -or- Floretion Algebra Multiplication Program, FAMP Code: 1kbasesumseq[A*B] with A = + 'i + 'ii' + 'ij' + 'ik' and B = + .5'i - .5'j + .5'k + .5i' + .5j' - .5k' - .5'ij' - .5'ik' + .5'ji' + .5'ki' Sumtype is set to: sum[(Y[0], Y[1], Y[2]),mod(3)
%t A110211 LinearRecurrence[{-5,0,6},{-1,3,-15},30] (* _Harvey P. Dale_, Mar 28 2012 *)
%Y A110211 Cf. A110210, A110212, A110213.
%K A110211 easy,sign,changed
%O A110211 0,2
%A A110211 _Creighton Dement_, Jul 16 2005