%I #15 Sep 08 2022 08:45:33
%S 1,7,39,239,1679,13439,120959,1209599,13305599,159667199,2075673599,
%T 29059430399,435891455999,6974263295999,118562476031999,
%U 2134124568575999,40548366802943999,810967336058879999
%N a(n) = n!/3 - 1.
%C Original definition: Natural numbers of the form (n! - 3)/3.
%H Vincenzo Librandi, <a href="/A139173/b139173.txt">Table of n, a(n) for n = 3..300</a>
%F E.g.f.: (6 - 3*x^2 - x^3)/(6*(1-x)) - exp(x). - _G. C. Greubel_, Oct 18 2018
%t Table[(n! - 3)/3, {n, 3, 20}]
%o (Magma) [Factorial(n)/3 -1: n in [3..25]]; // _Vincenzo Librandi_, Jul 20 2011
%o (PARI) for(n=3,25, print1((n!-3)/3, ", ")) \\ _G. C. Greubel_, Oct 18 2018
%Y Cf. A033312, A139172, A139173, A139174, A139175, A139176, A139177, A139183, A139184.
%Y Cf. A139191: primes in this sequence. - _M. F. Hasler_, Apr 09 2009
%K nonn
%O 3,2
%A _Artur Jasinski_, Apr 11 2008
%E Edited by _M. F. Hasler_, Apr 09 2009