

A075333


Pair up the natural numbers as (r, s) (say) so that all natural numbers are obtained only once as r, s, s+r, sr or r*s: (2, 3), (4, 11), (8, 17), (10, 22), (13, 27), (16, 34), ... Sequence gives first member of each pair.


5



2, 4, 8, 10, 13, 16, 19, 21, 23, 28, 30, 33, 36, 38, 42, 43, 48, 52, 54, 55, 60, 63, 65, 69, 71, 75, 77, 80, 82, 84, 87, 92, 94, 96, 98, 102, 104, 107, 111, 113, 116, 119, 121, 124, 126, 128, 134, 137, 140, 142, 144, 148, 150, 153, 154, 159, 162, 166, 168, 172, 174
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OFFSET

1,1


COMMENTS

The first pair starts with 2 and not with 1 as in (1,k) k occurs as 1*k (of the form r*s) and k (of the form s) itself, i.e., in two ways.


LINKS

Joshua Zucker, Feb 24 2008, Table of n, a(n) for n = 1..151


CROSSREFS

Cf. A075334, A075335, A075336, A075337.
Sequence in context: A154788 A219617 A100278 * A297250 A014190 A141400
Adjacent sequences: A075330 A075331 A075332 * A075334 A075335 A075336


KEYWORD

nonn


AUTHOR

Amarnath Murthy, Sep 18 2002


EXTENSIONS

Corrected and extended by Joshua Zucker, Feb 24 2008


STATUS

approved



