A326725 a(n) = (1/2)*n*(5*n - 7); row 5 of A326728.

0, -1, 3, 12, 26, 45, 69, 98, 132, 171, 215, 264, 318, 377, 441, 510, 584, 663, 747, 836, 930, 1029, 1133, 1242, 1356, 1475, 1599, 1728, 1862, 2001, 2145, 2294, 2448, 2607, 2771, 2940, 3114, 3293, 3477, 3666, 3860, 4059, 4263, 4472, 4686, 4905, 5129, 5358, 5592

Offset: 0

Author

Peter Luschny, Aug 04 2019

Keywords

• sign
• easy

Links

• Colin Barker, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

Crossrefs

Cf. A326728.

Programs

Maple

a := n -> (1/2)*n*(5*n - 7): seq(a(n), n=0..48);

PARI

concat(0, Vec(-x*(1 - 6*x) / (1 - x)^3 + O(x^40))) \\ Colin Barker, Aug 04 2019

Formula

From Colin Barker, Aug 04 2019: (Start)

G.f.: -x*(1 - 6*x)/(1 - x)^3.

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 2. (End)

E.g.f.: exp(x)*x*(5*x - 2)/2. - Elmo R. Oliveira, Dec 24 2024