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Search: id:A080275
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| A080275 |
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a(n)=(-1)^n(1 - (1/12)n(n + 1)(12 - n + n^2)). |
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+0
1
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| 1, 1, -6, 17, -39, 79, -146, 251, -407, 629, -934, 1341, -1871, 2547, -3394, 4439, -5711, 7241, -9062, 11209, -13719, 16631, -19986, 23827, -28199, 33149, -38726, 44981, -51967, 59739, -68354, 77871, -88351, 99857, -112454, 126209, -141191, 157471, -175122, 194219, -214839, 237061, -260966
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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a(n) is the determinant of the n X n matrix M with M(i,i)=2i-1, M(i,j)=i+j.
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FORMULA
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G.f.: (1 + 6x + 9x^2 + 7x^3 + x^4)/(1 + x)^5 a(n)=(-1)^n(1-A002378-A002415)
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MATHEMATICA
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CoefficientList[Series[(1 + 6x + 9x^2 + 7x^3 + x^4)/(1 + x)^5, {x, 0, 50}], x]
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CROSSREFS
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Sequence in context: A000385 A004799 A085278 this_sequence A061349 A101945 A013319
Adjacent sequences: A080272 A080273 A080274 this_sequence A080276 A080277 A080278
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KEYWORD
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easy,sign
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AUTHOR
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Mario Catalani (mario.catalani(AT)unito.it), Feb 12 2003
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