a(n) = T(n,n-5), array T as in A055807.

Terms

a(0) =1a(1) =31a(2) =80a(3) =160a(4) =280a(5) =450a(6) =681a(7) =985a(8) =1375a(9) =1865a(10) =2470a(11) =3206a(12) =4090a(13) =5140a(14) =6375a(15) =7815a(16) =9481a(17) =11395a(18) =13580a(19) =16060a(20) =18860a(21) =22006a(22) =25525a(23) =29445a(24) =33795a(25) =38605a(26) =43906a(27) =49730a(28) =56110a(29) =63080