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A082966 Number of inequivalent ways (mod D_4) three checkers can be placed on an n X n board. 6
0, 1, 16, 77, 319, 920, 2397, 5278, 10874, 20355, 36390, 61171, 99441, 154882, 235179, 346060, 499172, 702933, 974124, 1324585, 1777555, 2349116, 3070441, 3962762, 5066814, 6409975, 8044322, 10004463, 12355749, 15141190, 18441495, 22309336, 26843016, 32106217 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..34.

Erich Friedman, Illustration of initial terms

Index entries for linear recurrences with constant coefficients, signature (3,1,-11,6,14,-14,-6,11,-1,-3,1).

FORMULA

a(n) = 1/48*(n-1)*(n^5+n^4-2*n^3+14*n^2-5*n+3) if n is odd;

a(n) = 1/48*n*(n-1)*(n^2-n+2)*(n^2+2*n-2) if n is even.

G.f.: x^2*(x^8-x^7-4*x^6-55*x^5-56*x^4-83*x^3-28*x^2-13*x-1) / ((x-1)^7*(x+1)^4). - Colin Barker, Jul 11 2013

a(n) = A054247(n, 3) = A054247(n, n^2-3), n >= 1. - Wolfdieter Lang, Oct 03 2016

MATHEMATICA

Rest@ CoefficientList[Series[x^2*(x^8 - x^7 - 4 x^6 - 55 x^5 - 56 x^4 - 83 x^3 - 28 x^2 - 13 x - 1)/((x - 1)^7*(x + 1)^4), {x, 0, 34}], x] (* Michael De Vlieger, Oct 03 2016 *)

CROSSREFS

Cf. A014409, A054252, A242279, A242358, A054247.

Sequence in context: A007834 A228741 A200873 * A198182 A281466 A302620

Adjacent sequences:  A082963 A082964 A082965 * A082967 A082968 A082969

KEYWORD

nonn,easy

AUTHOR

Vladeta Jovovic, May 27 2003

EXTENSIONS

More terms from Colin Barker, Jul 11 2013

STATUS

approved

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Last modified January 25 01:49 EST 2020. Contains 331229 sequences. (Running on oeis4.)