a(n) = n*(n-1)*(2*n+1)*(2*n-1)*(2*n-3)*(10*n-17)/90.

Terms

a(0) =0a(1) =0a(2) =1a(3) =91a(4) =966a(5) =5082a(6) =18447a(7) =53053a(8) =129948a(9) =282948a(10) =562989a(11) =1043119a(12) =1824130a(13) =3040830a(14) =4868955a(15) =7532721a(16) =11313016a(17) =16556232a(18) =23683737a(19) =33201987a(20) =45713278a(21) =61927138a(22) =82672359a(23) =108909669a(24) =141745044a(25) =182443660