OFFSET
0,3
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
B. Runge, Codes and Siegel modular forms, Discrete Math. 148 (1996), 175-204, p. 202, last displayed formula.
Index entries for linear recurrences with constant coefficients, signature (1,1,0,-1,-1,2,-1,-1,0,1,1,-1).
FORMULA
a(n) ~ (1/108)*n^3 + (1/18)*n^2. - Ralf Stephan, Apr 29 2014
G.f.: ( 1+x^2-x+x^4 ) / ( (x^2-x+1)*(1+x)^2*(1+x+x^2)^2*(x-1)^4 ). - R. J. Mathar, Dec 18 2014
From Luce ETIENNE, Aug 14 2019: (Start)
a(n) = 4*a(n-6) - 6*a(n-12) + 4*a(n-18) - a(n-24).
a(n) = a(n-1) + a(n-2) - a(n-4) - a(n-5) + 2*a(n-6) - a(n-7) - a(n-8) + a(n-10) + a(n-11) - a(n-12).
a(n) = (240*floor(n/6)^3 + 60*(2*m+7)*floor(n/6)^2 - (16*m^5 - 205*m^4 + 930*m^3 - 1775*m^2 + 1034*m - 300)*floor(n/6) - 16*m^5 + 205*m^4 - 930*m^3 + 1775*m^2 - 1154*m + 120)/120 where m = n mod 6. (End)
MAPLE
(1 + x^3 + x^4 + x^5)/((1 - x^2)^2*(1 - x^3)*(1 - x^6));
MATHEMATICA
CoefficientList[ Series[ (1-x+x^2+x^4) / (1-x-x^2+x^4+x^5-2x^6+x^7+x^8-x^10-x^11+x^12), {x, 0, 52}], x] (* Jean-François Alcover, Dec 02 2011 *)
LinearRecurrence[{1, 1, 0, -1, -1, 2, -1, -1, 0, 1, 1, -1}, {1, 0, 2, 2, 4, 5, 9, 9, 15, 17, 23, 27}, 60] (* Harvey P. Dale, Dec 27 2016 *)
CROSSREFS
KEYWORD
nonn,nice,easy
AUTHOR
STATUS
approved