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A106389
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Numbers j such that 6j^2 + 6j + 1 = 13k.
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5
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1, 11, 14, 24, 27, 37, 40, 50, 53, 63, 66, 76, 79, 89, 92, 102, 105, 115, 118, 128, 131, 141, 144, 154, 157, 167, 170, 180, 183, 193, 196, 206, 209, 219, 222, 232, 235, 245, 248, 258, 261, 271, 274, 284, 287, 297, 300, 310, 313, 323, 326, 336, 339, 349, 352
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OFFSET
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1,2
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LINKS
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FORMULA
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j(1)=1, j(2)=11; then j(n)=j(n-2)+13.
a(n) = (-15+7*(-1)^n+26*n)/4. G.f.: x*(2*x^2+10*x+1) / ((x-1)^2*(x+1)). - Colin Barker, Apr 16 2014
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MATHEMATICA
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fQ[n_] := IntegerQ[(6n(n + 1) + 1)/13]; Select[ Range[ 361], fQ[ # ] &] (* Robert G. Wilson v, May 02 2005 *)
LinearRecurrence[{1, 1, -1}, {1, 11, 14}, 60] (* Harvey P. Dale, Jun 07 2016 *)
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PROG
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(PARI) Vec((2*x^2+10*x+1)/((x-1)^2*(x+1)) + O(x^100)) \\ Colin Barker, Apr 16 2014
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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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STATUS
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approved
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