69940

Appears in sequences

• 9-gonal (or enneagonal) pyramidal numbers: a(n) = n*(n+1)*(7*n-4)/6.at n=39A007584
• Numbers whose base-4 representation has exactly 9 runs.at n=21A043600
• Numbers n such that number of runs in the base 4 representation of n is congruent to 0 mod 9.at n=21A043858
• Numbers k such that number of runs in the base 4 representation of k is congruent to 9 mod 10.at n=21A043876
• Numbers k such that 7*2^k - 3 is prime.at n=42A058593
• Structured meta-anti-prism numbers, the n-th number from a structured n-gonal anti-prism number sequence.at n=19A100185
• Triangle read by rows: T(n,k) is number of paths from (0,0) to (3n,0) that stay in the first quadrant (but may touch the horizontal axis), consisting of steps u=(2,1), U=(1,2), or d=(1,-1) and having abscissa of first return equal to 3k.at n=21A108439
• Triangle read by rows: T(n,k) is number of paths from (0,0) to (3n,0) that stay in the first quadrant (but may touch the horizontal axis), consisting of steps u=(2,1),U=(1,2), or d=(1,-1) and having height of last peak equal to k.at n=43A109158
• Number of alternating separable permutations.at n=12A121703
• Even 9-gonal (nonagonal) pyramidal numbers.at n=28A218329