A091339 - OEIS

%I #11 Nov 25 2023 18:37:17

%S 1,2,3,8,27,220,5945,1307906,7775501177,10169624642405370,

%T 79073928376671158546120499,

%U 804152170591192270227367107671577224679640,63587471141272584754077292003976884470033921630214659882200111940371

%N a(n) = a(n-1)*a(n-2) + (n-2); a(1) = 1, a(2) = 2.

%C a(19) is a composite number with 1217 digits, and it has no prime factors < 10^9. - _Jianing Song_, Nov 25 2023

%H Jianing Song, <a href="/A091339/b091339.txt">Table of n, a(n) for n = 1..18</a>

%t a[1] = 1; a[2] = 2; a[n_] := a[n - 1]a[n - 2] + n - 2; Table[ a[n], {n, 13}] (* _Robert G. Wilson v_, Dec 10 2004 *)

%K nonn,easy

%O 1,2

%A Martti V. A. Holopainen (martti.holopainen(AT)pp2.inet.fi), Dec 06 2004

%E More terms from _Robert G. Wilson v_, Dec 10 2004