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A193624 Number of ways n triples can sit in a row without any siblings next to each other. 4
1, 0, 72, 37584, 53529984, 152458744320, 766958183193600, 6236531290739312640, 76788695692068062330880, 1361934174627779827740180480, 33454092372947487842682293452800, 1102556254139040688616563751190528000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n) approaches (3n)!*exp(-2) as n goes to infinity.

LINKS

Andrew Woods, Table of n, a(n) for n = 0..101

FORMULA

a(n) = A190826(n) * 6^n * n! for n >= 1. - Nathaniel Johnston, Aug 01 2011

Conjecture: a(n) +3*(-9*n^3+9*n^2-8*n-8)*a(n-1) +108*(n-1)*(n^2-11*n+16) *a(n-2) +3024*(n-1)*(n-2)^2*a(n-3) -5184*(n-1)*(n-2)*(n-3)*a(n-4)=0. - R. J. Mathar, May 23 2014

CROSSREFS

Cf. A007060.

Sequence in context: A062076 A284866 A153473 * A292198 A177326 A276014

Adjacent sequences: A193621 A193622 A193623 * A193625 A193626 A193627

KEYWORD

nonn

AUTHOR

Andrew Woods, Aug 01 2011

STATUS

approved

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Last modified December 6 08:31 EST 2022. Contains 358605 sequences. (Running on oeis4.)