A165623 Integers of the form a(n)=2^n/n^2.

2, 1, 1, 4, 256, 4194304, 4503599627370496, 20769187434139310514121985316880384, 1766847064778384329583297500742918515827483896875618958121606201292619776

Offset

1,1

Links

Table of n, a(n) for n=1..9.

Example

2^8/8^2=4, .. n :: 1,2,4,8,16,32,64,128,256,512,..

Mathematica

lst={}; Do[i=2^n/n^2; If[IntegerQ[i], AppendTo[lst, i]], {n, 6!}]; lst

Prog

(PARI) a(n)=2^(2^(n-1))/(2^(2*n-2))

Crossrefs

Cf. A007758

Sequence in context: A184880 A257859 A231622 * A374358 A264878 A338035

Adjacent sequences: A165620 A165621 A165622 * A165624 A165625 A165626

Keyword

nonn,easy

Author

Vladimir Joseph Stephan Orlovsky, Sep 22 2009

Extensions

Program by Charles R Greathouse IV, Oct 12 2009

Status

approved