199396

Appears in sequences

• Smallest triangular number containing exactly n 9's.at n=2A036526
• a(n) = (9n^4 - 18n^3 + 18n^2 - 9n + 2)/2.at n=14A079903
• Numerator of (9*(n^4 - 2*n^3 + 2*n^2 - n) + 2)/(2*(2*n-1)).at n=14A096430
• a(n) = A000217(A000217(n)+1).at n=35A267707
• Number of active (ON, black) cells at stage 2^n-1 of the two-dimensional cellular automaton defined by "Rule 411", based on the 5-celled von Neumann neighborhood.at n=8A271890