A069120 Integers of the form k!*sum(i=1..k, 1/(i*2^i) ).

4, 3489, 906408439650, 17919252390718041882750, 5699637429226533498825333877162500, 179263970680739996376691111034230475370480684738369155859375

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10

Example

4 is in the sequence because for k = 3, 3!*(1/1/2^1 + 1/2/2^2 + 1/3/2^3) = 4 is an integer. - Robert Israel, May 18 2014

Maple

select(type, [seq](k!*add(1/i/2^i, i=1..k), k=1..100), integer); # Robert Israel, May 18 2014

Crossrefs

Cf. A069119.

Sequence in context: A247154 A134908 A114498 * A221191 A110104 A024061

Adjacent sequences: A069117 A069118 A069119 * A069121 A069122 A069123

Keyword

easy,nonn

Author

Benoit Cloitre, Apr 07 2002

Status

approved