|
|
A052482
|
|
a(n) = 2^(n-2)*binomial(n+1,2).
|
|
6
|
|
|
3, 12, 40, 120, 336, 896, 2304, 5760, 14080, 33792, 79872, 186368, 430080, 983040, 2228224, 5013504, 11206656, 24903680, 55050240, 121110528, 265289728, 578813952, 1258291200, 2726297600, 5888802816, 12683575296, 27246198784, 58384711680, 124822487040
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
2,1
|
|
COMMENTS
|
Also the number of 4-cycles in the (n+1)-folded cube graph for n > 3. - Eric W. Weisstein, Mar 21 2018
|
|
LINKS
|
|
|
FORMULA
|
a(n) = (1/2) * Sum_{k=0..n-1} Sum_{i=0..n-1} (k+1) * C(n-1,i). - Wesley Ivan Hurt, Sep 20 2017
G.f.: x^2*(3 - 6*x + 4*x^2) / (1 - 2*x)^3.
a(n) = 2^(n-3)*n*(1 + n).
a(n) = 6*a(n-1) - 12*a(n-2) + 8*a(n-3) for n>4.
(End)
|
|
MATHEMATICA
|
CoefficientList[Series[(-3 + 6 x - 4 x^2)/(-1 + 2 x)^3, {x, 0, 20}], x] (* Eric W. Weisstein, Mar 21 2018 *)
|
|
PROG
|
(PARI) Vec(x^2*(3 - 6*x + 4*x^2) / (1 - 2*x)^3 + O(x^40)) \\ Colin Barker, Sep 22 2017
|
|
CROSSREFS
|
Cf. A301459 (6-cycles in the n-folded cube graph).
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|