Binomial(n, smallest odd prime factor of n).

Terms

a(0) =1a(1) =2a(2) =1a(3) =4a(4) =1a(5) =20a(6) =1a(7) =8a(8) =84a(9) =252a(10) =1a(11) =220a(12) =1a(13) =3432a(14) =455a(15) =16a(16) =1a(17) =816a(18) =1a(19) =15504a(20) =1330a(21) =705432a(22) =1a(23) =2024a(24) =53130a(25) =10400600a(26) =2925a(27) =1184040a(28) =1a(29) =4060