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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, 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
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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
