|
|
A065961
|
|
a(n) = (3*n - 1)!*n/2.
|
|
2
|
|
|
1, 120, 60480, 79833600, 217945728000, 1067062284288000, 8515157028618240000, 103408066955539906560000, 1814811575069725360128000000, 44208809968698509772718080000000, 1447219603135314415919699066880000000, 61998887798316869577999908025139200000000
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
a(n) = (3*n)! / 6.
a(n) - 3*n*(3*n-1)*(3*n-2)*a(n-1) = 0. - R. J. Mathar, Oct 31 2015
Sum_{n>=1} 1/a(n) = 2*e - 6 + 4*cos(sqrt(3)/2)/sqrt(e).
Sum_{n>=1} (-1)^(n+1)/a(n) = 6 - 2/e - 4*sqrt(e)*cos(sqrt(3)/2). (End)
|
|
MATHEMATICA
|
|
|
PROG
|
(PARI) { for (n=1, 60, a=(3*n - 1)!*n/2; write("b065961.txt", n, " ", a) ) } \\ Harry J. Smith, Nov 04 2009
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|