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A010012
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a(0) = 1, a(n) = 22*n^2 + 2 for n>0.
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1
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1, 24, 90, 200, 354, 552, 794, 1080, 1410, 1784, 2202, 2664, 3170, 3720, 4314, 4952, 5634, 6360, 7130, 7944, 8802, 9704, 10650, 11640, 12674, 13752, 14874, 16040, 17250, 18504, 19802, 21144, 22530, 23960, 25434, 26952, 28514, 30120, 31770, 33464, 35202, 36984
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OFFSET
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0,2
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COMMENTS
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Apart from the first term, numbers of the form (r^2+2*s^2)*n^2+2 = (r*n)^2+(s*n-1)^2+(s*n+1)^2: in this case is r=2, s=3. After 1, all terms are in A000408. (End)
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LINKS
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FORMULA
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MATHEMATICA
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Join[{1}, LinearRecurrence[{3, -3, 1}, {24, 90, 200}, 50]] (* Harvey P. Dale, Jul 20 2013 *)
CoefficientList[Series[(1 + x) (1 + 20 x + x^2)/(1 - x)^3, {x, 0, 50}], x] (* Vincenzo Librandi, Aug 03 2015 *)
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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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