|
|
A154030
|
|
Sequence defined by a(2*n) = 2*(n^2 + 2*n) and a(2*n-1) = (2*n)!/n!.
|
|
1
|
|
|
0, 2, 6, 12, 16, 120, 30, 1680, 48, 30240, 70, 665280, 96, 17297280, 126, 518918400, 160, 17643225600, 198, 670442572800, 240, 28158588057600, 286, 1295295050649600, 336, 64764752532480000, 390, 3497296636753920000, 448
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
LINKS
|
|
|
FORMULA
|
a(2*n) = 2*(n^2 + 2*n).
a(2*n-1) = (2*n)!/n!.
|
|
MATHEMATICA
|
Flatten[Table[{2*(n^2 - 1), (2*n)!/n!}, {n, 1, 20}]]
Table[If[EvenQ[n], 2*((n/2)^2 + n), (n+1)!/((n+1)/2)!], {n, 0, 30}] (* G. C. Greubel, Feb 08 2021 *)
|
|
PROG
|
(Sage)
if (n%2==0): return 2*((n/2)^2 + n)
else: return factorial(n+1)/factorial((n+1)/2)
(Magma) [ n mod 2 eq 0 select 2*((n/2)^2 + n) else Round(Factorial(n+1)/Gamma((n+3)/2)): n in [0..30]]; // G. C. Greubel, Feb 08 2021
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|