This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A173323 #21 Jan 24 2025 18:28:27
%S A173323 2,2,5,17,71,359,2159,15119,120959,1088639,10886399,119750399,
%T A173323 1437004799,18681062399,261534873599,3923023103999,62768369663999,
%U A173323 1067062284287999,19207121117183999,364935301226495999,7298706024529919999,153272826515128319999,3372002183332823039999
%N A173323 a(n) = 3*n! - 1.
%H A173323 Vincenzo Librandi, <a href="/A173323/b173323.txt">Table of n, a(n) for n = 0..200</a>
%F A173323 a(0)=2, a(n) = n*a(n-1)+n-1. - _Vincenzo Librandi_, Sep 30 2013
%F A173323 D-finite with recurrence a(n) +(-n-2)*a(n-1) +(2*n-1)*a(n-2) +(-n+2)*a(n-3)=0. - _R. J. Mathar_, Mar 07 2022
%F A173323 E.g.f.: 3/(1 - x) - exp(x). - _Stefano Spezia_, Oct 14 2024
%t A173323 Table[3 n! - 1, {n, 0, 25}] (* _Vincenzo Librandi_, Sep 30 2013 *)
%t A173323 3*(Range[0,20]!)-1 (* _Harvey P. Dale_, Oct 27 2015 *)
%o A173323 (Magma) [3*Factorial(n)-1: n in [0..25]]; // _Vincenzo Librandi_, Sep 30 2013
%o A173323 (Magma) [2] cat [n eq 1 select n+1 else n*Self(n-1)+n-1: n in [1..25] ]; // _Vincenzo Librandi_, Sep 30 2013
%Y A173323 Cf. sequences of the type k*n!-1: A033312 (k=1), A020543 (k=2), this sequence, A173321 (k=4), A173317 (k=5), A173316 (k=6).
%K A173323 nonn,easy
%O A173323 0,1
%A A173323 _Vincenzo Librandi_, Feb 16 2010