A057057 Let R(i,j) be the rectangle with antidiagonals 1; 2,3; 4,5,6; ...; C(n,3) is in antidiagonal a(n).

1, 3, 4, 6, 8, 11, 13, 15, 18, 21, 24, 27, 30, 33, 37, 40, 44, 48, 52, 55, 60, 64, 68, 72, 76, 81, 85, 90, 95, 100, 104, 109, 114, 119, 125, 130, 135, 141, 146, 152, 157, 163, 168, 174, 180, 186, 192, 198, 204, 210, 216, 223, 229

Offset: 3

Author

Clark Kimberling, Jul 30 2000

Keywords

• nonn

Crossrefs

Cf. A057045, A057062, A057048, A022846, A057054.

Programs

Mathematica

Table[Round[Sqrt[2*Binomial[n,3]]],{n,3,60}] (* Harvey P. Dale, Nov 16 2021 *)

Formula

Round(sqrt(2*binomial(n, 3))). - Vladeta Jovovic, Jun 14 2003