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A086955
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a(n) = n^2 + 2*n + 2 - (-1)^n.
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3
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1, 6, 9, 18, 25, 38, 49, 66, 81, 102, 121, 146, 169, 198, 225, 258, 289, 326, 361, 402, 441, 486, 529, 578, 625, 678, 729, 786, 841, 902, 961, 1026, 1089, 1158, 1225, 1298, 1369, 1446, 1521, 1602, 1681, 1766, 1849, 1938, 2025, 2118, 2209, 2306, 2401, 2502
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: (1 + 4*x - 3*x^2 + 2*x^3)/((1+x)*(1-x)^3).
a(2*n) = (2*n+1)^2 = A016754(n), a(2*n+1) = 4*n^2 + 8*n + 6 = A005899(n+1).
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MAPLE
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MATHEMATICA
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PROG
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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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