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A192264 a(1)=1, a(2)=2; a(n) = abs((n-1)*a(n-1) - n*a(n-2)), n > 2.

%I A192264 #14 Feb 23 2019 21:54:19
%S A192264 1,2,1,5,15,45,165,795,4875,35925,305625,2930775,31196175,364519425,
%T A192264 4635329325,63697629075,940361466675,14839587610125,249245709115425,
%U A192264 4438876720990575,83543374528387575,1656755577234346425,34527125085002707125
%N A192264 a(1)=1, a(2)=2; a(n) = abs((n-1)*a(n-1) - n*a(n-2)), n > 2.
%F A192264 a(n) = abs((n-1)*a(n-1) - n*a(n-2)), a(1) = 1, a(2) = 2.
%e A192264 a(3) = abs(a(2)*(3-1) - a(1)*3) = abs(2*2 - 1*3) =  1;
%e A192264 a(4) = abs(a(3)*(4-1) - a(2)*4) = abs(1*3 - 2*4) =  5;
%e A192264 a(5) = abs(a(4)*(5-1) - a(3)*5) = abs(5*4 - 1*5) = 15.
%p A192264 A192264 := proc(n) if n <=2 then n; else abs( (n-1)*procname(n-1)-n*procname(n-2)) ; end if; end proc: # _R. J. Mathar_, Jun 27 2011
%t A192264 a[1] = 1; a[2] = 2; a[n_] := a[n] = Abs[(n-1)*a[n-1] - n*a[n-2]]; Table[a[n], {n, 30}]
%o A192264 (MATLAB)
%o A192264 % n = number of computed terms of sequence
%o A192264 a(1)=1; a(2)=2;
%o A192264 for i=3:n,
%o A192264     a(i,1) = abs(a(i-1)*(i-1) - a(i-2)*i) ;
%o A192264 end
%K A192264 nonn
%O A192264 1,2
%A A192264 _Pasi Airikka_, Jun 27 2011
%E A192264 Corrected and edited by _R. J. Mathar_, Jun 27 2011