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.

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.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =4a(4) =9a(5) =23a(6) =65a(7) =201a(8) =679a(9) =2489a(10) =9831a(11) =41673a(12) =188858a(13) =911216a(14) =4664879a(15) =25265271a(16) =144350862a(17) =867748340a(18) =5475788662a(19) =36194252078a(20) =250093494424

External references