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A054497
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Number of symmetric nonnegative integer 7x7 matrices with sum of elements equal to 4*n, under action of dihedral group D_4.
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0
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1, 7, 31, 105, 300, 756, 1732, 3676, 7330, 13870, 25102, 43714, 73612, 120340, 191620, 298012, 453739, 677677, 994565, 1436435, 2044328, 2870296, 3979768, 5454280, 7394660, 9924668, 13195196, 17389028, 22726280, 29470520, 37935704
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| G.f.: 1/((1-x)^7*(1-x^2)^3).
a(0)=1, a(1)=7, a(2)=31, a(3)=105, a(4)=300, a(5)=756, a(6)=1732, a(7)=3676, a(8)=7330, a(9)=13870, a(10)=25102, a(11)=43714, a(12)=73612, a(n)= 7*a(n-1)-18*a(n-2)+14*a(n-3)+25*a(n-4)-63*a(n-5)+ 36*a(n-6)+ 36*a(n-7)- 63*a(n-8)+25*a(n-9)+14*a(n-10)-18*a(n-11)+ 7*a(n-12)- a(n-13) [From Harvey P. Dale, Feb 03 2012]
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MATHEMATICA
| CoefficientList[Series[1/((1-x)^7(1-x^2)^3), {x, 0, 30}], x] (* From Harvey P. Dale, Feb 03 2012 *)
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CROSSREFS
| Cf. A001753, A038163.
Sequence in context: A055899 A139876 A107392 * A119359 A055366 A160607
Adjacent sequences: A054494 A054495 A054496 * A054498 A054499 A054500
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KEYWORD
| nonn,changed
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), May 14 2000
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