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A265129 Triangle read by rows, formed as the sum of the two versions of the natural numbers filling an equilateral triangle. 1
2, 5, 5, 10, 10, 10, 17, 17, 17, 17, 26, 26, 26, 26, 26, 50, 50, 50, 50, 50, 50, 65, 65, 65, 65, 65, 65, 65, 82, 82, 82, 82, 82, 82, 82, 82, 101, 101, 101, 101, 101, 101, 101, 101, 101 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The natural numbers can sequentially fill a right- or left-handed equilateral triangle. Componentwise addition of the values of these two triangles produces the present triangle.

The row sums for this triangle give A034262.

The difference between the right- and left-handed triangles produces A049581.

LINKS

Table of n, a(n) for n=1..45.

Craig Knecht, Sum of right and left triangles.

Craig Knecht, Difference between right and left triangles A049581.

EXAMPLE

Displayed as a triangle:

   2;

   5  5;

  10 10 10;

  17 17 17 17;

  26 26 26 26 26;

  37 37 37 37 37 37;

  ...

CROSSREFS

Cf. A049581 (difference of triangles), A034262 (row sum of triangle), A069894 (center column).

Sequence in context: A059797 A173567 A288726 * A212624 A034387 A081240

Adjacent sequences:  A265126 A265127 A265128 * A265130 A265131 A265132

KEYWORD

nonn,tabl

AUTHOR

Craig Knecht, Dec 02 2015

STATUS

approved

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Last modified October 18 07:58 EDT 2019. Contains 328146 sequences. (Running on oeis4.)