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A095796
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1 + (26*n+17+7*n^2)*n/2.
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1
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1, 26, 98, 238, 467, 806, 1276, 1898, 2693, 3682, 4886, 6326, 8023, 9998, 12272, 14866, 17801, 21098, 24778, 28862, 33371, 38326, 43748, 49658, 56077, 63026, 70526, 78598, 87263, 96542, 106456
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OFFSET
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0,2
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COMMENTS
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Multiply the n-th power of the 4 X 4 matrix [1 0 0 0 / 1 1 0 0 / 2 3 1 0 / 6 12 7 1] by the column vector [1 1 1 1] from the right. Then a(n) is the last component of the vector that results, and A095794(n) the penultimate component.
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LINKS
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FORMULA
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a(n) = 4*a(n-1) -6*a(n-2) +4*a(n-3) -a(n-4).
G.f. ( 1+22*x-2*x^3 ) / (x-1)^4 . - R. J. Mathar, Nov 05 2011
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EXAMPLE
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806 = a(5) since M65 * [1 1 1 1] = [1 6 56 806] where 56 = A095794(5).
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MATHEMATICA
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LinearRecurrence[{4, -6, 4, -1}, {1, 26, 98, 238}, 40] (* Vincenzo Librandi, Jun 24 2012 *)
Table[1+(26n+17+7n^2)n/2, {n, 0, 30}] (* or *) CoefficientList[Series[ (1+ 22x- 2x^3)/(-1+x)^4, {x, 0, 30}], x]
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PROG
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(Magma) I:=[1, 26, 98, 238]; [n le 4 select I[n] else 4*Self(n-1)-6*Self(n-2)+4*Self(n-3)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Jun 24 2012
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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