If n = 2*m then a(n) = binomial(3*m, m)/(2*m+1), if n=2*m+1 then a(n) = binomial(3*m+1, m+1)/(2*m+1).

A047749

If n = 2*m then a(n) = binomial(3*m, m)/(2*m+1), if n=2*m+1 then a(n) = binomial(3*m+1, m+1)/(2*m+1).

Terms

    a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =7a(6) =12a(7) =30a(8) =55a(9) =143a(10) =273a(11) =728a(12) =1428a(13) =3876a(14) =7752a(15) =21318a(16) =43263a(17) =120175a(18) =246675a(19) =690690a(20) =1430715a(21) =4032015a(22) =8414640a(23) =23841480a(24) =50067108a(25) =142498692a(26) =300830572a(27) =859515920a(28) =1822766520a(29) =5225264024

External references