OFFSET
1,2
COMMENTS
The sequence lists the odd numbers ending with 1, 5 and 9. This follows from Mathar's generating function. - Bruno Berselli, Feb 16 2016
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 (1,0,1,-1).
FORMULA
G.f.: x - x^2*(-5-4*x-2*x^2+x^3) / ( (1+x+x^2)*(x-1)^2 ). - R. J. Mathar, Jul 15 2015
a(n) = 4*n - 2*floor(n/3 - 1/3) - 3. This formula follows from Mathar's generating function. - Bruno Berselli, Feb 16 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jul 10 2001
STATUS
approved