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A165420 a(1) = 1, a(2) = 2, a(n) = product of the previous terms for n >= 3.

%I A165420 #17 Oct 19 2018 03:19:36
%S A165420 1,2,2,4,16,256,65536,4294967296,18446744073709551616,
%T A165420 340282366920938463463374607431768211456,
%U A165420 115792089237316195423570985008687907853269984665640564039457584007913129639936
%N A165420 a(1) = 1, a(2) = 2, a(n) = product of the previous terms for n >= 3.
%C A165420 Same as A001146 with 1 and 2 added in front. - _Stanislav Sykora_, Oct 05 2014
%H A165420 G. C. Greubel, <a href="/A165420/b165420.txt">Table of n, a(n) for n = 1..14</a>
%F A165420 a(1) = 1, a(2) = 2, a(n) = Product_{i=1..n-1} a(i), n >= 3.
%F A165420 a(1) = 1, a(2) = 2, a(n) = A000079(2^(n-3)) = A001146(n-3) = 2^(2^(n-3)), n >= 3.
%F A165420 a(1) = 1, a(2) = 2, a(3) = 2, a(n) = (a(n-1))^2, n >= 4.
%t A165420 a[1]:= 1; a[2]:= 2; a[n_]:= Product[a[j], {j,1,n-1}]; Table[a[n], {n, 1, 12}] (* _G. C. Greubel_, Oct 19 2018 *)
%o A165420 (PARI) {a(n) = if(n==1, 1, if(n==2, 2, prod(j=1, n-1, a(j))))};
%o A165420 for(n=1, 10, print1(a(n), ", ")) \\ _G. C. Greubel_, Oct 19 2018
%Y A165420 Cf. A000079, A001146.
%K A165420 nonn
%O A165420 1,2
%A A165420 _Jaroslav Krizek_, Sep 17 2009