a(n) = binomial(n, floor(n/5)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =5a(6) =6a(7) =7a(8) =8a(9) =9a(10) =45a(11) =55a(12) =66a(13) =78a(14) =91a(15) =455a(16) =560a(17) =680a(18) =816a(19) =969a(20) =4845a(21) =5985a(22) =7315a(23) =8855a(24) =10626a(25) =53130a(26) =65780a(27) =80730a(28) =98280a(29) =118755