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Search: id:A014983
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| A014983 |
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a(n) = a(n-1) + (-3)^(n-1) = (1 - (-3)^n)/4. G.f.: x/((1-x)*(1+3*x)). |
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9
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| 0, 1, -2, 7, -20, 61, -182, 547, -1640, 4921, -14762, 44287, -132860, 398581, -1195742, 3587227, -10761680, 32285041, -96855122, 290565367, -871696100, 2615088301, -7845264902, 23535794707, -70607384120, 211822152361, -635466457082
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OFFSET
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0,3
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COMMENT
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q-integers for q=-3.
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 927
R. A. Sulanke, Moments of generalized Motzkin paths, J. Integer Sequences, Vol. 3 (2000), #00.1.
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FORMULA
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a(n) = the (1, 2)-th element of M^n, where M = ((1, 1, 1, -2), (1, 1, -2, 1), (1, -2, 1, 1), (-2, 1, 1, 1)). - Simone Severini (ss54(AT)york.ac.uk), Nov 25 2004
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PROGRAM
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(PARI) a(n)=(1-(-3)^n)/4
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CROSSREFS
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A014983(n)=-(-1)^n*A015518(n).
Sequence in context: A116950 A111017 A116408 this_sequence A015518 A083379 A000935
Adjacent sequences: A014980 A014981 A014982 this_sequence A014984 A014985 A014986
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KEYWORD
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sign,easy
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AUTHOR
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Olivier Gerard (ogerard(AT)ext.jussieu.fr)
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