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A240525
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a(n) = 2^(n-2)*(2^(n+4)-(-1)^n+5).
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1
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5, 19, 68, 268, 1040, 4144, 16448, 65728, 262400, 1049344, 4195328, 16780288, 67112960, 268447744, 1073758208, 4295016448, 17179934720, 68719673344, 274878169088, 1099512414208, 4398047559680, 17592189190144, 70368748371968, 281474989293568, 1125899923619840
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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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G.f.: (5-x-28*x^2)/(1-4*x-4*x^2+16*x^3).
a(n) = 4*a(n-1) + 4*a(n-2)- 16*a(n-3) with n>2, a(0)=5, a(1)=19, a(2)=68.
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MATHEMATICA
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CoefficientList[Series[(5 - x - 28 x^2)/(1 - 4 x - 4 x^2 + 16 x^3), {x, 0, 33}], x]
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PROG
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(Magma) [2^(n-2)*(2^(n+4)-(-1)^n+5): n in [0..25]] /* or */ I:=[5, 19, 68]; [n le 3 select I[n] else 4*Self(n-1)+4*Self(n-2)-16*Self(n-3): n in [1..30]]
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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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