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

Terms

a(0) =1a(1) =-1a(2) =-4a(3) =-1a(4) =21a(5) =29a(6) =-80a(7) =-244a(8) =153a(9) =1473a(10) =836a(11) =-6920a(12) =-12220a(13) =23209a(14) =91213a(15) =-21511a(16) =-510680a(17) =-457965a(18) =2210520a(19) =4921941a(20) =-6271749a(21) =-33288595a(22) =-3876765a(23) =173223185a(24) =214943855a(25) =-682969376a(26) =-1912499375a(27) =1498348275a(28) =11882164650a(29) =5332839025