A165423 a(1) = 1, a(2) = 5, a(n) = product of the previous terms for n >= 3.

1, 5, 5, 25, 625, 390625, 152587890625, 23283064365386962890625, 542101086242752217003726400434970855712890625

Offset: 1

Author

Jaroslav Krizek, Sep 17 2009

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..13

Programs

Mathematica

a[1]:= 1; a[2]:= 5; a[n_]:= Product[a[j], {j,1,n-1}]; Table[a[n],{n,1, 12}] (* G. C. Greubel, Oct 19 2018 *)

PARI

{a(n) = if(n==1, 1, if(n==2, 5, prod(j=1,n-1, a(j))))};
for(n=1,10, print1(a(n), ", ")) \\ G. C. Greubel, Oct 19 2018

Formula

a(1) = 1, a(2) = 5, a(n) = Product_{i=1..n-1} a(i), n >= 3.

a(1) = 1, a(2) = 5, a(n) = A000351(2^(n-3)) = 5^(2^(n-3)), n >= 3.

a(1) = 1, a(2) = 5, a(3) = 5, a(n) = (a(n-1))^2, n >= 4.