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A259755 Numbers that are congruent to {4,20} mod 24. 7
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Danny Rorabaugh, Table of n, a(n) for n = 1..10000

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

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

MATHEMATICA

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 *)

PROG

(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

CROSSREFS

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

KEYWORD

nonn,easy

AUTHOR

José María Grau Ribas, Jul 18 2015

EXTENSIONS

Better name from Danny Rorabaugh, Oct 22 2015

STATUS

approved

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Last modified January 24 02:16 EST 2021. Contains 340398 sequences. (Running on oeis4.)