A071962 Number of double points of the map that, for each term t of a sequence, counts the preceding terms that are greater than or equal to t.

1, 2, 4, 10, 26, 70, 216, 682, 2264, 7960, 29262, 113256, 452586, 1886306, 8109828, 36274448, 167157176

Offset

0,2

Comments

It would be nice to have a formula or recurrence!

Links

Table of n, a(n) for n=0..16.

Zoran Sunic, Young tableaux and other mutually describing sequences, Journal of Integer Sequences, Vol. 5 (2002), Article 02.1.5

Zoran Sunic, Self-Describing Sequences and the Catalan Family Tree, Electronic Journal of Combinatorics, 10 (2003) #N5.

Example

The ten double points for n=3 form the following 5 pairs: (0000,0123), (0003,0120), (0020,0103), (0023,0100), (0021,0101)

Crossrefs

Sequence in context: A085455 A055226 A097085 * A257520 A035079 A259206

Adjacent sequences: A071959 A071960 A071961 * A071963 A071964 A071965

Keyword

nonn,more

Author

Zoran Sunic, Jun 24 2002

Extensions

More terms from John W. Layman, Jul 01 2002

Status

approved