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A091018 Numbers in n-th upward diagonal of triangle T : 0; 1, 2; 3, 4, 5; 6, 7, 8, 9; ... 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

See also A090894 (downward diagonal).

LINKS

Table of n, a(n) for n=0..70.

FORMULA

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

EXAMPLE

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

PROG

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

CROSSREFS

Sequence in context: A260220 A249742 A246276 * A248971 A329435 A160795

Adjacent sequences:  A091015 A091016 A091017 * A091019 A091020 A091021

KEYWORD

easy,nonn

AUTHOR

Philippe Deléham, Feb 25 2004

STATUS

approved

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Last modified June 20 06:56 EDT 2021. Contains 345157 sequences. (Running on oeis4.)