A202552 Number of n-element nonnegative integer arrays that are ascent sequences (interior element no greater than one plus up-steps preceding it) in both forward and reverse directions

1, 1, 2, 4, 9, 23, 65, 201, 679, 2489, 9831, 41673, 188858, 911216, 4664879, 25265271, 144350862, 867748340, 5475788662, 36194252078, 250093494424, 1803204139718, 13543620370665, 105800880875545, 858375849401380, 7222921375625584

Offset

1,3

Links

R. H. Hardin, Table of n, a(n) for n = 1..116

Example

Some solutions for n=7
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....1....1....0....1....0....0....1....1....1....0....1....0....0....1....1
..1....1....0....1....0....0....0....2....2....0....1....0....1....1....0....1
..2....1....0....0....1....0....1....1....1....0....1....2....0....2....0....1
..1....0....1....1....2....0....0....0....0....1....1....2....0....2....2....1
..1....0....0....1....1....0....1....1....0....1....0....1....0....1....1....1
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0

Crossrefs

Sequence in context: A245161 A245162 A007476 * A272301 A359032 A129698

Adjacent sequences: A202549 A202550 A202551 * A202553 A202554 A202555

Keyword

nonn

Author

R. H. Hardin Dec 21 2011

Status

approved