a(n)=If[IntegerQ[((3*n - 2)/( n + 1))*a(n - 1)], ((3*n - 2)/(n + 1))* a(n - 1), If[IntegerQ[((4*n - 2)/(n + 1))*a( n - 1)], ((4*n - 2)/(n + 1))*a(n - 1), n*a(n - 1)]].
A155580
a(n)=If[IntegerQ[((3*n - 2)/( n + 1))*a(n - 1)], ((3*n - 2)/(n + 1))* a(n - 1), If[IntegerQ[((4*n - 2)/(n + 1))*a( n - 1)], ((4*n - 2)/(n + 1))*a(n - 1), n*a(n - 1)]].
Terms
- a(0) =1a(1) =1a(2) =2a(3) =5a(4) =10a(5) =30a(6) =180a(7) =585a(8) =1430a(9) =3575a(10) =9100a(11) =31850a(12) =83300a(13) =220150a(14) =792540a(15) =11888100a(16) =32167800a(17) =87567900a(18) =1576222200a(19) =4334611050a(20) =11971782900a(21) =33194488950a(22) =92367273600a(23) =257858638800a(24) =722004188640
External references
- oeis: A155580