OFFSET
1,1
LINKS
William A. Stein, Dimensions of the spaces S_k^{new}(Gamma_0(N))
William A. Stein, The modular forms database
Index entries for linear recurrences with constant coefficients, signature (0,1,1,0,-1).
FORMULA
a(n) = a(n-2)+a(n-3)-a(n-5) for n>6. G.f.: x*(4+11*x+15*x^2+12*x^3+5*x^4-x^5)/((1 -x)^2*(1 +x)*(1 +x +x^2)). - Colin Barker, Sep 27 2012
MATHEMATICA
a[n_] := a[n] = If[n <= 6, {4, 11, 19, 27, 35, 41}[[n]], a[n-2] + a[n-3] - a[n-5]]; Array[a, 50] (* Jean-François Alcover, Dec 06 2016 after Colin Barker *)
PROG
(PARI) a(n)=if(n>1, ([0, 1, 0, 0, 0; 0, 0, 1, 0, 0; 0, 0, 0, 1, 0; 0, 0, 0, 0, 1; -1, 0, 1, 1, 0]^(n-1)*[5; 11; 19; 27; 35])[1, 1], 4) \\ Charles R Greathouse IV, Nov 27 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jul 10 2001
STATUS
approved