213488

Appears in sequences

• a(n+3) = a(n+2) + a(n+1) + a(n) - 4.at n=21A000803
• Rook polynomials.at n=19A004306
• Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 21.at n=22A031699
• a(n) = 441n^2 + 2n.at n=21A158321
• a(n) is the denominator corresponding to A376736(n).at n=6A376737