A216628 a(n) = A163085(n)/n!.

1, 1, 1, 2, 3, 18, 60, 1200, 10500, 735000, 18522000, 4667544000, 359400888000, 332086420512000, 81408613942656000, 279394363051195392000, 224737840779305293440000, 2892376010829659126572800000, 7812628980363223707442752000000, 379850021025259936655866602240000000

Offset: 0

Author

Peter Luschny, Sep 18 2012

Keywords

• nonn

Crossrefs

Cf. A056040.

Programs

Sage

def A216628(n):
    swing = lambda n: factorial(n)/factorial(n//2)^2
    A163085 = lambda n: mul(swing(i) for i in (0..n))
    return A163085(n)/factorial(n)
[A216628(n) for n in (0..19)]