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A181858 a(n) = lcm(n^2, n!) / lcm(n^2, swinging_factorial(n)). 1
1, 1, 1, 1, 1, 4, 4, 36, 18, 64, 576, 14400, 43200, 518400, 518400, 5080320, 12700800, 1625702400, 1625702400, 131681894400, 131681894400, 627056640000, 13168189440000, 1593350922240000 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,6
COMMENTS
A divisibility sequence, i.e., if m|n then a(m)|a(n). Except for n = 9 the prime factors of A181858(n) are the primes <= floor((n-1)/2). Using this fact the divisibility property can be proved. - Peter Luschny, Jan 10 2011
LINKS
FORMULA
a(n) = A181857(n) / A181860(n).
MAPLE
A181858 := n -> `if`(n=0, 1, ilcm(n^2, n!)/ilcm(n^2, n!/iquo(n, 2)!^2));
MATHEMATICA
a[n_] := If[n == 0, 1, LCM[n^2, n!]/LCM[n^2, n!/Quotient[n, 2]!^2]];
Table[a[n], {n, 0, 23}] (* Jean-François Alcover, Jun 18 2019 *)
PROG
(PARI) a(n)=lcm(n^2, n!)/lcm(n!/(n\2)!^2, n^2) \\ Charles R Greathouse IV, Feb 01 2013
CROSSREFS
Sequence in context: A222504 A226008 A145109 * A227511 A249807 A180064
KEYWORD
nonn
AUTHOR
Peter Luschny, Nov 21 2010
STATUS
approved

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Last modified March 29 11:14 EDT 2024. Contains 371278 sequences. (Running on oeis4.)