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%I #23 Mar 05 2022 01:44:43
%S 1,2,1,0,-1,-4,-19,-110,-751,-5898,-52331,-517412,-5639201,-67153000,
%T -867349799,-12075744186,-180268812991,-2872225263670,-48647560669399,
%U -872783866785512,-16534245908255329,-329812134298321068,-6909520574356487099,-151679640501544395110
%N a(n+2) = n*a(n+1) - a(n), with a(1)=1, a(2)=2.
%C Starting with offset 5 unsigned: (1, 4, 19, 110, 751, ...) = eigensequence of triangle A003991. - _Gary W. Adamson_, May 17 2010
%H Seiichi Manyama, <a href="/A075374/b075374.txt">Table of n, a(n) for n = 1..451</a>
%F a(n+1) = (a(n) + a(n+2))/n with a(1) = 1, a(2) = 2.
%p a[1] := 1:a[2] := 2:for n from 1 to 45 do a[n+2] := n*a[n+1]-a[n]:od:seq(a[i],i=1..45);
%t a[n_]:= a[n]= If[n<3, n, (n-2)*a[n-1] -a[n-2]];
%t Table[a[n], {n,50}] (* _G. C. Greubel_, Mar 04 2022 *)
%o (Magma) [n le 2 select n else (n-2)*Self(n-1) - Self(n-2): n in [1..50]]; // _G. C. Greubel_, Mar 04 2022
%o (Sage)
%o @CachedFunction
%o def a(n): return n if (n<3) else (n-2)*a(n-1) - a(n-2) # A075374
%o [a(n) for n in (1..50)] # _G. C. Greubel_, Mar 04 2022
%Y Cf. A003991. - _Gary W. Adamson_, May 17 2010
%K sign
%O 1,2
%A _Amarnath Murthy_, Sep 20 2002
%E More terms from _Sascha Kurz_, Jan 30 2003
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