A161788 a(n) is the largest integer of the form 2^k - 1 that divides n.

1, 1, 3, 1, 1, 3, 7, 1, 3, 1, 1, 3, 1, 7, 15, 1, 1, 3, 1, 1, 7, 1, 1, 3, 1, 1, 3, 7, 1, 15, 31, 1, 3, 1, 7, 3, 1, 1, 3, 1, 1, 7, 1, 1, 15, 1, 1, 3, 7, 1, 3, 1, 1, 3, 1, 7, 3, 1, 1, 15, 1, 31, 63, 1, 1, 3, 1, 1, 3, 7, 1, 3, 1, 1, 15, 1, 7, 3, 1, 1, 3, 1, 1, 7, 1, 1, 3, 1, 1, 15, 7, 1, 31, 1, 1, 3, 1, 7, 3, 1, 1

Offset: 1

Author

Leroy Quet, Jun 19 2009

Keywords

• nonn

Comments

a(n) = 2^A161789(n) - 1.

a(A161790(n)) = 1.

Crossrefs

Cf. A000225, A161789, A161790.

Programs

Maple

A161788 := proc(n) for k from ilog2(n+1) to 0 by -1 do if n mod (2^k-1) = 0 then RETURN(2^k-1); fi; od: end: seq(A161788(n),n=1..120) ; # R. J. Mathar, Jun 27 2009

Extensions

Extended by R. J. Mathar, Jun 27 2009