OFFSET
1,1
LINKS
William A. Stein, Dimensions of the spaces S_k(Gamma_0(N)).
William A. Stein, The modular forms database
Index entries for linear recurrences with constant coefficients, signature (1,1,-1).
FORMULA
a(n) = 10*n-a(n-1)-12 for n>2, with a(1)=2, a(2)=7. [Vincenzo Librandi, Aug 07 2010]
a(n) = (-7+(-1)^n+10*n)/2. a(n)=a(n-1)+a(n-2)-a(n-3) for n>4. G.f.: x*(x^3 +2*x^2 +5*x +2) / ((x -1)^2*(x +1)). - Colin Barker, Sep 08 2013
MATHEMATICA
LinearRecurrence[{1, 1, -1}, {2, 7, 11, 17}, 50] (* Harvey P. Dale, Oct 09 2019 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jul 08 2001
STATUS
approved