A118016 Integers of the form 2^k/(k-1).

4, 4, 8, 64, 8192, 268435456, 576460752303423488, 5316911983139663491615228241121378304, 904625697166532776746648320380374280103671755200316906558262375061821325312

Offset

1,1

Links

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

Formula

a(n) = 4*A016031(n). - Paolo P. Lava, Nov 10 2006

Example

k=5: 2^5/(5-1) = 32/4 = 8.
k=17: 2^17/(17-1) = 131072/16 = 8192.

Maple

P:=proc(n) local i, j; for i from 2 by 1 to n do j:=2^i/(i-1); if trunc(j)=j then print(j); fi; od; end: P(5000);

Mathematica

f[n_]:=2^n/n*2; Select[Table[f[n], {n, 4, 6!}], IntegerQ] (* Vladimir Joseph Stephan Orlovsky, Dec 05 2009 *)
Select[Table[2^n/(n-1), {n, 2, 500}], IntegerQ] (* Harvey P. Dale, Sep 27 2024 *)

Crossrefs

Cf. A016031 (de Bruijn's sequence: 2^(2^(n-1) - n)).

Sequence in context: A298569 A281717 A205971 * A201989 A071775 A269594

Adjacent sequences: A118013 A118014 A118015 * A118017 A118018 A118019

Keyword

nonn

Author

Paolo P. Lava and Giorgio Balzarotti, May 11 2006

Status

approved