Number of n-element subsets of [n+9] having an even sum.

Terms

a(0) =1a(1) =5a(2) =25a(3) =110a(4) =365a(5) =1001a(6) =2485a(7) =5720a(8) =12190a(9) =24310a(10) =46126a(11) =83980a(12) =147070a(13) =248710a(14) =408430a(15) =653752a(16) =1021735a(17) =1562275a(18) =2343055a(19) =3453450a(20) =5008003a(21) =7153575a(22) =10079355a(23) =14024400a(24) =19284460a(25) =26225628a(26) =35302540a(27) =47071640a(28) =62203340a(29) =81505820