28855

Appears in sequences

• 9-gonal (or enneagonal) pyramidal numbers: a(n) = n*(n+1)*(7*n-4)/6.at n=29A007584
• Triangle read by rows: T(n,k) is the number of hill-free Dyck paths of semilength n and having k peaks at level 2; 0<= k<=n-1, n>=2 (a Dyck path is said to be hill-free if it has no peaks at level 1).at n=65A114626
• Number of hill-free Dyck paths of semilength n+3 and having no peaks at level 2 (a Dyck path is said to be hill-free if it has no peaks at level 1).at n=9A114627
• Odd 9-gonal (nonagonal) pyramidal numbers.at n=7A218328
• a(n) is the smallest n-gonal pyramidal number with binary weight n.at n=6A358931