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A169598
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Numbers that are congruent to {3,18} mod 23.
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1
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3, 18, 26, 41, 49, 64, 72, 87, 95, 110, 118, 133, 141, 156, 164, 179, 187, 202, 210, 225, 233, 248, 256, 271, 279, 294, 302, 317, 325, 340, 348, 363, 371, 386, 394, 409, 417, 432, 440, 455, 463, 478, 486, 501, 509, 524, 532, 547, 555, 570, 578, 593, 601, 616, 624
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OFFSET
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1,1
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COMMENTS
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Conjecture: For no n in the sequence 36*n^2+72*n+35 = (6*n+5)*(6*n+7) is of the form p*(p+2), where p and p+2 are primes.
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LINKS
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FORMULA
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a(n) = (46*n + 7*(-1)^n - 27)/4. - Vincenzo Librandi, Jan 06 2013, modified Jul 07 2015
G.f.: x*(3+15*x+5*x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Jul 07 2015
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MAPLE
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MATHEMATICA
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Select[Range[624], MemberQ[{3, 18}, Mod[#, 23]]&] (* Ray Chandler, Jul 08 2015 *)
LinearRecurrence[{1, 1, -1}, {3, 18, 26}, 55] (* Ray Chandler, Jul 08 2015 *)
Rest[CoefficientList[Series[x*(3+15*x+5*x^2)/((1+x)*(x-1)^2), {x, 0, 55}], x]] (* Ray Chandler, Jul 08 2015 *)
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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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Added leading terms. Clarified comment. - R. J. Mathar, Jul 07 2015
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STATUS
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approved
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