OFFSET
0,5
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (2,0,-1,-1,1,0,-1,1,1,0,-2,1).
FORMULA
G.f.: -x^3*(x^4+x^2+x+1) / ((x-1)^5*(x+1)*(x^2+x+1)*(x^4+x^3+x^2+x+1)).
EXAMPLE
For n=4 the 3 partitions of 2*4 = 8 are [1,1,1,1,4], [1,1,1,2,3] and [1,1,2,2,2].
MATHEMATICA
CoefficientList[Series[- x^3 (x^4 + x^2 + x + 1) / ((x - 1)^5 (x + 1) (x^2 + x + 1) (x^4 + x^3 + x^2 + x + 1)), {x, 0, 50}], x] (* Vincenzo Librandi, Mar 22 2015 *)
LinearRecurrence[{2, 0, -1, -1, 1, 0, -1, 1, 1, 0, -2, 1}, {0, 0, 0, 1, 3, 7, 13, 23, 37, 57, 84, 119}, 50] (* Harvey P. Dale, Mar 06 2023 *)
PROG
(PARI) concat(0, vector(40, n, k=0; forpart(p=2*n, k++, , [5, 5]); k))
(PARI) concat([0, 0, 0], Vec(-x^3*(x^4+x^2+x+1)/((x-1)^5*(x+1)*(x^2+x+1)*(x^4+x^3+x^2+x+1)) + O(x^100)))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Mar 22 2015
STATUS
approved