A139802 a(1)=1, a(2)=2, a(n)=n^a(n-2).

1, 2, 3, 16, 125, 2821109907456, 4337654948097993282537354757263188251697832994620405101744893017744569432720994168089672192211758909320807

Offset: 1

Author

Paolo P. Lava and Giorgio Balzarotti, May 22 2008

Keywords

• easy
• nonn

Comments

Exponential double factorial.

The next term is too large to include.

Examples

			a(1)=1;
a(2)=2;
a(3)=3^1=3;
a(4)=4^2=16;
a(5)=5^3=125;
a(6)=6^16=2821109907456;
etc.
		

Crossrefs

Cf. A049384.

Programs

Mathematica

a[1]=1; a[2]=2; a[n_]:=n^a[n-2]; Array[a,7] (* Stefano Spezia, Feb 14 2024 *)