A130011 A self-describing sequence. Pick any integer n in the sequence; this n says: "There are n terms in the sequence that are <= 3n". This sequence is the slowest increasing one with this property.

1, 4, 5, 12, 15, 16, 17, 18, 19, 20, 21, 36, 37, 38, 45, 48, 51, 54, 57, 60, 63, 64, 65, 66, 67, 68, 69

Offset

1,2

Comments

See comments in A094591 and A037988.

It is not clear in what sense "slowest increasing" is meant in the description of this sequence. The definition requires that there be exactly a(k) terms <= 3 a(k), for any index k. Therefore, a(n+1) > 3n for all indices n of the form n = a(k). Thus, any such sequence has an infinite number of terms a(k) >= 3k-2. The lexicographically first variant A260107, which starts (1, 4, 5, 6, 13, 16, 19, 20, 21, 22, ...), also has all its terms a(k) <= 3k-2, so it cannot be said to increase faster. - M. F. Hasler, Jul 16 2015

Links

Table of n, a(n) for n = 1..27

Crossrefs

Sequence in context: A047608 A266725 A308783 * A050022 A137619 A115375

Adjacent sequences: A130008 A130009 A130010 * A130012 A130013 A130014

Keyword

more,nonn

Author

Eric Angelini, Jun 15 2007

Status

approved