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A275970
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a(n) = 3*2^n + n - 1.
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2
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2, 6, 13, 26, 51, 100, 197, 390, 775, 1544, 3081, 6154, 12299, 24588, 49165, 98318, 196623, 393232, 786449, 1572882, 3145747, 6291476, 12582933, 25165846, 50331671, 100663320, 201326617, 402653210, 805306395, 1610612764, 3221225501, 6442450974, 12884901919, 25769803808, 51539607585, 103079215138, 206158430243, 412316860452, 824633720869
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n) = 2*a(n-1) - n + 2.
O.g.f.: (2 - 2*x - x^2)/( (1-2*x)*(1-x)^2 ).
E.g.f.: 3*exp(2*x) + (x-1)*exp(x).
a(n) = 4*a(n-1) - 5*a(n-2) + 2*a(n-2). (End)
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MATHEMATICA
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LinearRecurrence[{4, -5, 2}, {2, 6, 13}, 25] (* or *) Table[3*2^n + n - 1, {n, 0, 25}] (* G. C. Greubel, Aug 18 2016 *)
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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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