a(n) = Sum_{k=0..floor(n/10)} (-1)^k * binomial(n-5*k,5*k).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =1a(8) =1a(9) =1a(10) =0a(11) =-5a(12) =-20a(13) =-55a(14) =-125a(15) =-251a(16) =-461a(17) =-791a(18) =-1286a(19) =-2001a(20) =-3001a(21) =-4356a(22) =-6121a(23) =-8281a(24) =-10626a(25) =-12500a(26) =-12340a(27) =-6885a(28) =10110a(29) =49875