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A290027 Number of 4-cycles in the n-halved cube graph. 3
0, 0, 3, 102, 900, 5160, 23520, 92736, 330624, 1094400, 3421440, 10222080, 29432832, 82188288, 223641600, 595230720, 1554186240, 3990749184, 10097197056, 25214976000, 62234296320, 151993712640, 367691563008, 881823055872, 2098200576000, 4956409036800 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..26.

Eric Weisstein's World of Mathematics, Graph Cycle

Eric Weisstein's World of Mathematics, Halved Cube Graph

Index entries for linear recurrences with constant coefficients, signature (10, -40, 80, -80, 32).

FORMULA

a(n) = 3*2^(n-5)*binomial(n,3)*(13*n-35).

a(n) = 10*a(n-1)-40*a(n-2)+80*a(n-3)-80*a(n-4)+32*a(n-5).

G.f.: (-3*x*(x^2 + 24*x^3))/(-1 + 2*x)^5.

MATHEMATICA

Table[3 2^(n - 5) Binomial[n, 3] (13 n - 35), {n, 20}]

LinearRecurrence[{10, -40, 80, -80, 32}, {0, 0, 3, 102, 900}, 20]

CoefficientList[Series[-((3 (x^2 + 24 x^3))/(-1 + 2 x)^5), {x, 0, 20}], x]

CROSSREFS

Cf. A290026 (3-cycles), A290028 (5-cycles), A290029 (6-cycles).

Sequence in context: A108220 A130733 A037062 * A224817 A157549 A157566

Adjacent sequences:  A290024 A290025 A290026 * A290028 A290029 A290030

KEYWORD

nonn

AUTHOR

Eric W. Weisstein, Jul 17 2017

STATUS

approved

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Last modified June 25 10:09 EDT 2021. Contains 345453 sequences. (Running on oeis4.)