81221

Appears in sequences

• 9-gonal (or enneagonal) pyramidal numbers: a(n) = n*(n+1)*(7*n-4)/6.at n=41A007584
• a(n) = (8*n+3)*(8*n+7).at n=35A146301
• a(n) = 100*n^2 + 100*n + 21.at n=28A152161
• Odd 9-gonal (nonagonal) pyramidal numbers.at n=10A218328