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 A107851 #22 Mar 14 2024 15:20:12
%S A107851 0,1,1,4,4,5,9,10,18,29,41,68,100,149,233,346,530,813,1225,1876,2852,
%T A107851 4325,6601,10026,15250,23229,35305,53732,81764,124341,189225,287866,
%U A107851 437906,666317,1013641,1542132,2346276,3569413,5430537,8261962,12569362
%N A107851 Expansion of g.f. x*(-1-x-3*x^2-x^3+2*x^5)/((2*x^3+x^2-1)*(x^4+1)).
%C A107851 Floretion Algebra Multiplication Program, FAMP Code: 1jesforzapseq[(.5i' + .5j' + .5'ki' + .5'kj')*(.5'i + .5'j + .5'ik' + .5'jk')], 1vesforzap = A000004
%H A107851 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (0,1,2,-1,0,1,2).
%F A107851 a(n) = A159284(n+1) + A132380(n+7).
%F A107851 a(0)=0, a(1)=1, a(2)=1, a(3)=4, a(4)=4, a(5)=5, a(6)=9, a(n)= a(n-2)+ 2*a(n-3)-a(n-4)+a(n-6)+2*a(n-7). - _Harvey P. Dale_, Jul 19 2011
%t A107851 CoefficientList[Series[x(-1-x-3x^2-x^3+2x^5)/((2x^3+x^2-1)(x^4+1)), {x,0,50}],x] (* or *) LinearRecurrence[{0,1,2,-1,0,1,2},{0,1,1,4,4,5,9},51] (* _Harvey P. Dale_, Jul 19 2011 *)
%o A107851 (PARI) a(n)=([0,1,0,0,0,0,0; 0,0,1,0,0,0,0; 0,0,0,1,0,0,0; 0,0,0,0,1,0,0; 0,0,0,0,0,1,0; 0,0,0,0,0,0,1; 2,1,0,-1,2,1,0]^n*[0;1;1;4;4;5;9])[1,1] \\ _Charles R Greathouse IV_, Oct 03 2016
%Y A107851 Cf. A107849, A107850, A107852.
%K A107851 easy,nonn
%O A107851 0,4
%A A107851 _Creighton Dement_, May 25 2005