A091018 Numbers in n-th upward diagonal of triangle T : 0; 1, 2; 3, 4, 5; 6, 7, 8, 9; ...

0, 1, 3, 2, 6, 4, 10, 7, 5, 15, 11, 8, 21, 16, 12, 9, 28, 22, 17, 13, 36, 29, 23, 18, 14, 45, 37, 30, 24, 19, 55, 46, 38, 31, 25, 20, 66, 56, 47, 39, 32, 26, 78, 67, 57, 48, 40, 33, 27, 91, 79, 68, 58, 49, 41, 34, 105, 92, 80, 69, 59, 50, 42, 35, 120, 106, 93, 81, 70, 60, 51

Offset: 0

Author

Philippe Deléham, Feb 25 2004

Keywords

• easy
• nonn

Comments

See also A090894 (downward diagonal).

Examples

			0; 1; 3,2; 6,4; 10,7,5; 15,11,8; 21,16,12,9; 28,22,17,13; ...
		

Programs

PARI

T(n,k)=(n-k)^2+(n+k) /* Michael Somos, May 31 2005 */

Formula

a(n) = A056536(n+1) - 1.