A259752 a(n) = 24*n - 18.

6, 30, 54, 78, 102, 126, 150, 174, 198, 222, 246, 270, 294, 318, 342, 366, 390, 414, 438, 462, 486, 510, 534, 558, 582, 606, 630, 654, 678, 702, 726, 750, 774, 798, 822, 846, 870, 894, 918, 942, 966, 990, 1014, 1038, 1062, 1086, 1110, 1134, 1158, 1182, 1206

Offset: 1

Author

José María Grau Ribas, Jul 12 2015

Keywords

• nonn
• easy

Comments

Original name: Numbers n such that n/A259748(n) = 6.

Partial sums give A152746. - Leo Tavares, Jul 29 2023

Links

• Danny Rorabaugh, Table of n, a(n) for n = 1..10000
• Index entries for linear recurrences with constant coefficients, signature (2,-1).

Crossrefs

Cf. A000914, A016813, A063128, A063148, A152746.

Other sequences of numbers n such that A259748(n)/n equals a constant: A008606, A073762, A259749, A259750, A259751, A259754, A259755.

Programs

Mathematica

A[n_] := A[n] = Sum[a b, {a, 1,  n}, {b, a + 1, n}] ; Select[Range[600], Mod[A[#], #]/# == 1/6 & ]

Formula

A259748(a(n))/a(n) = 1/6.

a(n) = 6*A016813(n-1). - Michel Marcus, Jul 18 2015

G.f.: 6*x*(3*x+1)/(x-1)^2. - Alois P. Heinz, Jul 29 2023

From Elmo R. Oliveira, Apr 04 2025: (Start)

E.g.f.: 6*(exp(x)*(4*x - 3) + 3).

a(n) = 2*a(n-1) - a(n-2) for n > 2. (End)

Extensions

Better name from Danny Rorabaugh, Oct 22 2015