OFFSET
2,2
COMMENTS
Without the restriction "non-equivalent (mod D_3)" the numbers are given by A234250.
LINKS
Heinrich Ludwig, Table of n, a(n) for n = 2..1000
Index entries for linear recurrences with constant coefficients, signature (3,0,-7,3,6,0,-6,-3,7,0,-3,1)
FORMULA
a(n) = (n^6 + 3*n^5 - 3*n^4 + 10*n^3 - 48*n^2 + IF(n==1 mod 2)*(27*n^2 - 45*n - 9) + IF(n==1 mod 3)*64)/288.
G.f.: x^3*(x^7-x^6-2*x^5-15*x^4-13*x^3-16*x^2-10*x-4) / ((x-1)^7*(x+1)^3*(x^2+x+1)). - Colin Barker, Feb 14 2014
MATHEMATICA
LinearRecurrence[{3, 0, -7, 3, 6, 0, -6, -3, 7, 0, -3, 1}, {0, 4, 22, 82, 231, 566, 1216, 2410, 4428, 7712, 12780, 20392}, 40] (* Harvey P. Dale, Dec 09 2021 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Heinrich Ludwig, Feb 13 2014
STATUS
approved