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A175976
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a(n) = 4^n-3*n+1.
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1
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2, 2, 11, 56, 245, 1010, 4079, 16364, 65513, 262118, 1048547, 4194272, 16777181, 67108826, 268435415, 1073741780, 4294967249, 17179869134, 68719476683, 274877906888, 1099511627717, 4398046511042, 17592186044351, 70368744177596
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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.: ( -2+10*x-17*x^2 ) / ( (4*x-1)*(x-1)^2 ).
a(n)-6*a(n-1)+9*a(n-2)-4*a(n-3) = 0 for n>2.
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EXAMPLE
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a(1)=4-3+1=2. a(2)=16-6+1=11.
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MAPLE
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A175976 := proc(n) 4^n-3*n+1 ; end proc:
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MATHEMATICA
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Table[4^n-3n+1, {n, 0, 30}] (* or *) LinearRecurrence[{6, -9, 4}, {2, 2, 11}, 30] (* Harvey P. Dale, Jul 07 2013 *)
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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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EXTENSIONS
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G.f., program and link to recurrences from R. J. Mathar, Nov 03 2010
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STATUS
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approved
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