Number of compositions of 5*n-1 into parts 2 and 5.

Terms

a(0) =1a(1) =3a(2) =7a(3) =18a(4) =52a(5) =154a(6) =450a(7) =1301a(8) =3753a(9) =10838a(10) =31327a(11) =90568a(12) =261813a(13) =756786a(14) =2187496a(15) =6323023a(16) =18277014a(17) =52830706a(18) =152709940a(19) =441415867a(20) =1275934888a(21) =3688154521a(22) =10660798289a(23) =30815580241a(24) =89074003241a(25) =257472939209a(26) =744238632362