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1, 5, 9, 37, 113, 261, 505, 869, 1377, 2053, 2921, 4005, 5329, 6917, 8793, 10981, 13505, 16389, 19657, 23333, 27441, 32005, 37049, 42597, 48673, 55301, 62505, 70309, 78737, 87813, 97561, 108005, 119169, 131077, 143753, 157221, 171505, 186629, 202617, 219493
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OFFSET
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-1,2
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COMMENTS
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Squares in the sequence: 1, 9, 5329, for n = -1, 1, 11 respectively. No other square for n < 9*10^9.
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LINKS
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FORMULA
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G.f.: (-1 + 9*x - 17*x^2 + 35*x^3 - 2*x^4)/(1 - x)^4.
a(n) = 4*a(n-1)-6*a(n-2)+4*a(n-3)-a(n-4) for n>3.
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MAPLE
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MATHEMATICA
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Table[4 n^3 + 5, {n, -1, 50}] (* or *) CoefficientList[Series[(-1 + 9 x - 17 x^2 + 35 x^3 - 2 x^4)/(1 - x)^4, {x, 0, 40}], x]
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PROG
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(Magma) [4*n^3+5: n in [-1..40]]; /* or */ I:=[1, 5, 9, 37]; [n le 4 select I[n] else 4*Self(n-1)-6*Self(n-2)+4*Self(n-3)-Self(n-4): n in [1..40]]
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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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