|
|
A126804
|
|
a(n) = (2n)! / (n-1)!.
|
|
14
|
|
|
2, 24, 360, 6720, 151200, 3991680, 121080960, 4151347200, 158789030400, 6704425728000, 309744468633600, 15543540607795200, 841941782922240000, 48962152914554880000, 3042648073975910400000, 201220459292273541120000, 14110584707870682071040000
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
Old name was "Multiplying n X n integers above n".
|
|
LINKS
|
|
|
FORMULA
|
a(n) = (2n)! / (n-1)!.
a(n) = (2*n*(2*n-1)/(n-1))*a(n-1).
E.g.f.: 2*x/(1-4*x)^(3/2). (End)
|
|
EXAMPLE
|
a(5) = 151200 because five digits above 5: (6, 7, 8, 9, 10), multiplied by five equals 5*(6*7*8*9*10) = 151200.
|
|
MAPLE
|
a:=n->sum((count(Permutation(2*n+2), size=n+1)), j=0..n): seq(a(n), n=0..15); # Zerinvary Lajos, May 03 2007
with(combstruct):with(combinat) :bin := {B=Union(Z, Prod(B, B))}: seq (count([B, bin, labeled], size=n)*(n-1), n=2..17); # Zerinvary Lajos, Dec 05 2007
|
|
MATHEMATICA
|
|
|
PROG
|
(Magma) [Factorial(2*n)/Factorial(n-1) : n in [1..20]]; // Wesley Ivan Hurt, Dec 14 2015
(PARI) x='x+O('x^99); Vec(serlaplace(2*x/(1-4*x)^(3/2))) \\ Altug Alkan, Mar 11 2018
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Jonathan R. Love (japanada11(AT)yahoo.ca), Feb 22 2007
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|