A205958 a(0) = 1 and a(n) = A180000(n)*a(floor(n/2))^2 for n > 0.

1, 1, 1, 1, 2, 2, 3, 3, 48, 16, 40, 40, 270, 270, 945, 63, 129024, 129024, 64512, 64512, 2016000, 96000, 528000, 528000, 144342000, 28868400, 187644600, 20849400, 1787836050, 1787836050, 59594535, 59594535, 3999321544458240, 121191561953280, 1030128276602880

Offset: 0

Author

Peter Luschny, Feb 04 2012

Keywords

• nonn

Comments

lcm(1,2,..,n) = (n!*a(n)) / ((n/2)!*a(n/2))^2.

lcm(1,2,..,n)*a(n) is a divisor of n! and n!/(lcm(1,2,..,n)*a(n)) is a square.

Crossrefs

Cf. A180000, A025527, A205959.

Programs

Sage

def A205958(n) :
    if n == 0 : return 1
    return A180000(n)*A205958(n//2)^2