A090894 Numbers in n-th downward diagonal of triangle T : 0; 1, 2; 3, 4, 5; 6, 7, 8, 9; ...

0, 1, 2, 3, 4, 6, 5, 7, 10, 8, 11, 15, 9, 12, 16, 21, 13, 17, 22, 28, 14, 18, 23, 29, 36, 19, 24, 30, 37, 45, 20, 25, 31, 38, 46, 55, 26, 32, 39, 47, 56, 66, 27, 33, 40, 48, 57, 67, 78, 34, 41, 49, 58, 68, 79, 91, 35, 42, 50, 59, 69, 80, 92, 105, 43, 51, 60, 70, 81, 93, 106, 120

Offset: 0

Author

Philippe Deléham, Feb 25 2004

Keywords

• easy
• nonn

Comments

Also the skewed triangle read by nonzero columns:

1, 2

0, 3, 4, 5

0, 0, 6, 7, 8, 9

0, 0, 0, 10,11,12,13,14

... (offset 0,0), - Ralf Stephan, Mar 09 2014

Crossrefs

See also A091018 (upward diagonal).

Formula

a(n) = A091995(n+1)-1.

As skewed triangle: T(n,k) = (n+1)*(n+2)/2 + k-n, for n <= k <= 2n+2. - Ralf Stephan, Mar 09 2014