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 A104187 #26 Mar 06 2024 15:47:55
%S A104187 1,3,8,18,38,76,147,279,523,973,1802,3328,6136,11302,20805,38285,
%T A104187 70437,129575,238348,438414,806394,1483216,2728087,5017763,9229135,
%U A104187 16975057,31222030
%N A104187 Expansion of g.f. -(1+x^2+x^4)/((x^3+x^2+x-1)*(x-1)^2).
%C A104187 A floretion-generated sequence involving tribonacci numbers.
%C A104187 Floretion Algebra Multiplication Program, FAMP Code: 1tesforrokseq[A*B] = A = - .5'ii' + .5'jj' + .5'kk' + .5e B = + 'kj', 1vesforrokseq[A*B] = A000004, ForType: 1A.
%H A104187 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2,0,-1,1).
%F A104187 a(n+2) - 2*a(n+1) + a(n) = A081172(n+4).
%F A104187 a(n) = (1/2) [A000073(n+3) + A000073(n+6) - 3n - 6 ]. - _Ralf Stephan_, May 20 2007
%F A104187 a(0)=1, a(1)=3, a(2)=8, a(3)=18, a(4)=38, a(n) = 3*a(n-1) - 2*a(n-2) - a(n-4) + a(n-5). - _Harvey P. Dale_, Jun 14 2011
%t A104187 CoefficientList[Series[-(1+x^2+x^4)/((x^3+x^2+x-1)*(x-1)^2), {x,0,30}], x] (* or *) LinearRecurrence[{3,-2,0,-1,1},{1,3,8,18,38},30] (* _Harvey P. Dale_, Jun 14 2011 *)
%Y A104187 Cf. A081172.
%K A104187 nonn
%O A104187 0,2
%A A104187 _Creighton Dement_, Apr 01 2005
%E A104187 Definition corrected by _Harvey P. Dale_, Jun 14 2011