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A179808 Number of n X 3 arrays with every diagonal and antidiagonal of length L containing a permutation of 1..L. 1
0, 1, 4, 9, 12, 25, 60, 121, 220, 441, 924, 1849, 3612, 7225, 14620, 29241, 58140, 116281, 233244, 466489, 931612, 1863225, 3729180, 7458361, 14911260, 29822521, 59655964, 119311929, 238602012, 477204025, 954451740, 1908903481, 3817719580 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,3

LINKS

R. H. Hardin, Table of n, a(n) for n=3..99

FORMULA

Empirical: a(n) = 2*a(n-1)-a(n-2)+2*a(n-3)+2*a(n-4)-4*a(n-5); G.f.: -(-x-2*x^2-2*x^3+4*x^4)*x^3 / (1-2*x+x^2-2*x^3-2*x^4+4*x^5).

EXAMPLE

All solutions for 5 X 3:

.1.1.1...1.1.1...1.2.1...1.2.1

.2.2.2...2.3.2...1.3.1...1.2.1

.3.3.3...2.3.2...2.3.2...3.3.3

.1.2.1...1.3.1...2.3.2...2.2.2

.1.2.1...1.2.1...1.1.1...1.1.1

CROSSREFS

Sequence in context: A076794 A254520 A283105 * A083351 A055381 A287498

Adjacent sequences:  A179805 A179806 A179807 * A179809 A179810 A179811

KEYWORD

nonn

AUTHOR

R. H. Hardin, formula from Alois P. Heinz in the Sequence Fans Mailing List, Jul 28 2010

STATUS

approved

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Last modified December 12 22:06 EST 2019. Contains 329963 sequences. (Running on oeis4.)