a(n) = product of those positive integers which are coprime to both n and n+1 and which are <= n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =1a(5) =5a(6) =15a(7) =35a(8) =7a(9) =189a(10) =35a(11) =385a(12) =1485a(13) =143a(14) =1001a(15) =2027025a(16) =5005a(17) =85085a(18) =459459a(19) =46189a(20) =20995a(21) =1249937325a(22) =1616615a(23) =7436429a(24) =324342711a(25) =71504125a(26) =132793375a(28) =7436429a(29) =215656441a(31) =75969882625