A139173 a(n) = n!/3 - 1.

1, 7, 39, 239, 1679, 13439, 120959, 1209599, 13305599, 159667199, 2075673599, 29059430399, 435891455999, 6974263295999, 118562476031999, 2134124568575999, 40548366802943999, 810967336058879999

Offset: 3

Author

Artur Jasinski, Apr 11 2008

Keywords

• nonn

Comments

Original definition: Natural numbers of the form (n! - 3)/3.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 3..300

Crossrefs

Cf. A033312, A139172, A139173, A139174, A139175, A139176, A139177, A139183, A139184.

Cf. A139191: primes in this sequence. - M. F. Hasler, Apr 09 2009

Programs

Magma

[Factorial(n)/3 -1: n in [3..25]]; // Vincenzo Librandi, Jul 20 2011

Mathematica

Table[(n! - 3)/3, {n, 3, 20}]

PARI

for(n=3,25, print1((n!-3)/3, ", ")) \\ G. C. Greubel, Oct 18 2018

Formula

E.g.f.: (6 - 3*x^2 - x^3)/(6*(1-x)) - exp(x). - G. C. Greubel, Oct 18 2018

Extensions

Edited by M. F. Hasler, Apr 09 2009