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A111328 a(0)=1, a(1)=2; a(2n) = 2*a(2n-1)+1; a(2n+1) = a(2n) + x, where x is the least number not yet the difference of two terms. 0
1, 2, 5, 7, 15, 22, 45, 54, 109, 120, 241, 253, 507, 523, 1047, 1065, 2131, 2150, 4301, 4323, 8647, 8671, 17343, 17368, 34737, 34763, 69527, 69554, 139109, 139137, 278275, 278304, 556609, 556640, 1113281, 1113314, 2226629, 2226663, 4453327 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Each positive integer can be represented exactly once as the difference of two terms.

LINKS

Table of n, a(n) for n=0..38.

Paul Erd├Ás, Problem E3202, American Mathematical Monthly, 94(1987), 372. [N. Sato, Oct 14 2008]

EXAMPLE

a(4) = 2*a(3)+1 = 15,

a(5) = a(4)+7 = 22 because 7 is not yet a difference.

CROSSREFS

Sequence in context: A215513 A306956 A337655 * A244962 A022629 A032216

Adjacent sequences:  A111325 A111326 A111327 * A111329 A111330 A111331

KEYWORD

easy,nonn

AUTHOR

Holger Stephan (stephan(AT)wias-berlin.de), Nov 04 2005

EXTENSIONS

Edited by Don Reble, May 16 2006

Definition corrected by Guy P. Srinivasan, Dec 11 2006

STATUS

approved

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Last modified May 25 18:25 EDT 2022. Contains 354071 sequences. (Running on oeis4.)