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Search: id:A157706
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| A157706 |
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The z^2 coefficients of the polynomials in the GF1 denominators of A156921. |
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+0
2
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| 7, 75, 385, 1365, 3850, 9282, 19950, 39270, 72105, 125125, 207207, 329875, 507780, 759220, 1106700, 1577532, 2204475, 3026415, 4089085, 5445825, 7158382, 9297750, 11945050, 15192450, 19144125, 23917257
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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See A157702 for background information.
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FORMULA
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a(n) = 7*a(n-1)-21*a(n-2)+35*a(n-3)-35*a(n-4)+21*a(n-5)-7*a(n-6)+a(n-7)
a(n) = 1/18*n^6+1/6*n^5+1/72*n^4-1/4*n^3-5/72*n^2+1/12*n
G.f.: (7+26*z+7*z^2)/(1-z)^7
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MAPLE
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nmax:=27; for n from 0 to nmax do fz(n):= product( (1-(2*m-1)*z)^(n+1-m) , m=1..n); c(n):= coeff(fz(n), z, 2); end do: a:=n-> c(n): seq(a(n), n=2..nmax);
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CROSSREFS
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Cf. A156921, A157702.
Sequence in context: A097821 A054745 A106162 this_sequence A127190 A121316 A066302
Adjacent sequences: A157703 A157704 A157705 this_sequence A157707 A157708 A157709
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KEYWORD
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easy,nonn
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AUTHOR
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Johannes W. Meijer (meijgia(AT)hotmail.com), Mar 07 2009
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