|
%I #14 Aug 26 2019 14:24:05
%S 1,4,4,16,256,65536,4294967296,18446744073709551616,
%T 340282366920938463463374607431768211456,
%U 115792089237316195423570985008687907853269984665640564039457584007913129639936
%N a(1) = 1, a(2) = 4, a(n) = product of the previous terms for n >= 3.
%H Vincenzo Librandi, <a href="/A165422/b165422.txt">Table of n, a(n) for n = 1..13</a>
%F a(1) = 1, a(2) = 4, a(n) = Product_{i=1..n-1} a(i), n >= 3.
%F a(1) = 1, a(2) = 4, a(n) = A000302(2^(n-3)) = A001146(n-2) = 2^(2^(n-2)), n >= 3.
%F a(1) = 1, a(2) = 4, a(3) = 4, a(n) = (a(n-1))^2, n >= 4.
%t a[1]:= 1; a[2]:= 4; a[n_] := Product[a[j], {j,1,n-1}]; Table[a[n], {n,1,12}] (* _G. C. Greubel_, Oct 19 2018 *)
%t Join[{1,4},NestList[#^2&,4,10]] (* _Harvey P. Dale_, Aug 26 2019 *)
%o (PARI) {a(n) = if(n==1, 1, if(n==2, 4, prod(j=1,n-1, a(j))))};
%o for(n=1,10, print1(a(n), ", ")) \\ _G. C. Greubel_, Oct 19 2018
%K nonn
%O 1,2
%A _Jaroslav Krizek_, Sep 17 2009
|
