A071910 - OEIS

A071910

a(n) = t(n)*t(n+1)*t(n+2), where t() are the triangular numbers.

0, 18, 180, 900, 3150, 8820, 21168, 45360, 89100, 163350, 283140, 468468, 745290, 1146600, 1713600, 2496960, 3558168, 4970970, 6822900, 9216900, 12273030, 16130268, 20948400, 26910000, 34222500, 43120350, 53867268, 66758580, 82123650, 100328400, 121777920

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OFFSET

0,2

COMMENTS

a(n) is also the number of three-dimensional cage assemblies such that the assembly is not a cube. See also A052149 for the two-dimensional version and to A059827 for the non-exclusive version. - Alejandro Rodriguez, Oct 20 2020

LINKS

Table of n, a(n) for n=0..30.

Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).

FORMULA

a(n) = 18*A006542(n+3). - Vladeta Jovovic, Jun 14 2002

G.f.: 18*x*(1+3*x+x^2)/(1-x)^7. - Vladeta Jovovic, Jun 14 2002

a(n) = ((n+1)*(n+2))^3/8 - Sum_{i=1..n+1} i^3. - Jon Perry, Feb 13 2004

a(n) = C(2+n, n)*C(3+n, 1+n)*C(4+n, 2+n). - Zerinvary Lajos, Jul 29 2005

a(n) = A059827(n+1) - A000537(n+1). - Michel Marcus, Oct 21 2015

PROG

(PARI) t(n) = n*(n+1)/2;

a(n) = t(n)*t(n+1)*t(n+2); \\ Michel Marcus, Oct 21 2015

CROSSREFS

Cf. A006542, (first differences of a(n) /18) A006414, (second differences of a(n) /18) A006322, (third differences of a(n) /18) A004068, (fourth differences of a(n) /18) A005891, (fifth differences of a(n) /18) A008706.

Sequence in context: A239581 A213350 A052507 * A121038 A341370 A004410

Adjacent sequences: A071907 A071908 A071909 * A071911 A071912 A071913

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Jun 13 2002

STATUS

approved