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A259755
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Numbers that are congruent to {4,20} mod 24.
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7
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4, 20, 28, 44, 52, 68, 76, 92, 100, 116, 124, 140, 148, 164, 172, 188, 196, 212, 220, 236, 244, 260, 268, 284, 292, 308, 316, 332, 340, 356, 364, 380, 388, 404, 412, 428, 436, 452, 460, 476, 484, 500, 508, 524, 532, 548, 556, 572, 580, 596, 604, 620, 628
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refs;
listen;
history;
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OFFSET
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1,1
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LINKS
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Danny Rorabaugh, Table of n, a(n) for n = 1..10000
Index entries for linear recurrences with constant coefficients, signature (1,1,-1).
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FORMULA
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a(n) = 2*(6*n + (-1)^n - 3).
A259748(a(n))/a(n) = 3/4.
a(n) = 4*A007310(n). - Michel Marcus, Sep 22 2015
G.f.: 4*x*(1 + 4*x + x^2) / ((1 + x)*(1 - x)^2). - Bruno Berselli, Oct 23 2015
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MATHEMATICA
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A[n_] := A[n] = Sum[a b, {a, 1, n}, {b, a + 1, n}]; Select[Range[200], Mod[A[#], #]/# == 3/4 &]
Table[2 (6 n + (-1)^n - 3), {n, 1, 60}] (* Bruno Berselli, Oct 23 2015 *)
LinearRecurrence[{1, 1, -1}, {4, 20, 28}, 60] (* Harvey P. Dale, Jul 19 2016 *)
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PROG
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(MAGMA) [2*(6*n+(-1)^n-3): n in [1..60]]; // Vincenzo Librandi, Aug 27 2015
(PARI) vector(100, n, 2*(6*n+(-1)^n-3)) \\ Altug Alkan, Oct 23 2015
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CROSSREFS
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Cf. A000914, A007310.
Other sequences of numbers n such that A259748(n)/n equals a constant: A008606, A073762, A259749, A259750, A259751, A259752, A259754.
Sequence in context: A202070 A198831 A323040 * A317249 A181433 A079454
Adjacent sequences: A259752 A259753 A259754 * A259756 A259757 A259758
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KEYWORD
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nonn,easy
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AUTHOR
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José María Grau Ribas, Jul 18 2015
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EXTENSIONS
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Better name from Danny Rorabaugh, Oct 22 2015
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STATUS
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approved
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