a(n) = 25*binomial(n-1,6) + binomial(n-1,5).

Terms

a(0) =0a(1) =1a(2) =31a(3) =196a(4) =756a(5) =2226a(6) =5502a(7) =12012a(8) =23892a(9) =44187a(10) =77077a(11) =128128a(12) =204568a(13) =315588a(14) =472668a(15) =689928a(16) =984504a(17) =1376949a(18) =1891659a(19) =2557324a(20) =3407404a(21) =4480630a(22) =5821530a(23) =7480980a(24) =9516780a(25) =11994255a(26) =14986881a(27) =18576936a(28) =22856176a(29) =27926536