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A255877
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a(n) = (2n-2)^3 + (2n-2) - 1.
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0
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-1, 9, 67, 221, 519, 1009, 1739, 2757, 4111, 5849, 8019, 10669, 13847, 17601, 21979, 27029, 32799, 39337, 46691, 54909, 64039, 74129, 85227, 97381, 110639, 125049, 140659, 157517, 175671, 195169, 216059, 238389, 262207, 287561, 314499, 343069, 373319
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OFFSET
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1,2
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COMMENTS
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a(n)/a(n-1) tends to 1 as n becomes very large (of order 10^3 or more).
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LINKS
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FORMULA
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a(n) = (2*n-2)^3 + (2*n-2) - 1.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4. - Vincenzo Librandi, Mar 17 2015
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EXAMPLE
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a(3) = (2*3-2)^3 + (2*3-2) - 1 = 67.
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MATHEMATICA
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PROG
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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