cp's OEIS Frontend

A073889 a(1) = 1, a(2) = 3; for n>2, a(n) = {a(n-1)*a(n+1)}^(1/n) or a(n+1) = a(n)^n/a(n-1).

%I A073889 #9 Jan 25 2025 19:00:46
%S A073889 1,3,9,243,387420489,35917545547686059365808220080151141317043
%N A073889 a(1) = 1, a(2) = 3; for n>2, a(n) = {a(n-1)*a(n+1)}^(1/n) or a(n+1) = a(n)^n/a(n-1).
%p A073889 A073889:= proc(n) option remember;
%p A073889 if n<3 then 2*n-1;
%p A073889 else a(n-1)^(n-1)/a(n-2);
%p A073889 fi; end;
%p A073889 seq(A073889(n), n = 1..7); # _G. C. Greubel_, May 18 2020
%t A073889 a[n_]:= a[n]= If[n<3, 2*n-1, a[n-1]^(n-1)/a[n-2]]; Table[a[n], {n, 7}] (* _G. C. Greubel_, May 18 2020 *)
%o A073889 (Magma) I:=[1,3]; [n le 2 select I[n] else Self(n-1)^(n-1)/Self(n-2): n in [1..7]]; // _G. C. Greubel_, May 18 2020
%o A073889 (Sage)
%o A073889 def a(n):
%o A073889     if (n<3): return 2*n-1
%o A073889     else: return a(n-1)^(n-1)/a(n-2)
%o A073889 [a(n) for n in (1..7)] # _G. C. Greubel_, May 18 2020
%Y A073889 Cf. A058798, A073888.
%K A073889 nonn
%O A073889 1,2
%A A073889 _Amarnath Murthy_, Aug 17 2002
%E A073889 The next term is too large to include.