A132118 Triangle read by rows: T(n,k) = n*(n-1)/2 + 2*k - 1.

1, 2, 4, 4, 6, 8, 7, 9, 11, 13, 11, 13, 15, 17, 19, 16, 18, 20, 22, 24, 26, 22, 24, 26, 28, 30, 32, 34, 29, 31, 33, 35, 37, 39, 41, 43, 37, 39, 41, 43, 45, 47, 49, 51, 53, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76

Offset: 1

Author

Gary W. Adamson, Aug 10 2007

Keywords

• nonn
• easy
• tabl

Examples

			First few rows of the triangle are:
   1;
   2,  4;
   4,  6,  8;
   7,  9, 11, 13;
  11, 13, 15, 17, 19;
  16, 18, 20, 22, 24, 26;
  22, 24, 26, 28, 30, 32, 34;
  29, 31, 33, 35, 37, 39, 41, 43;
  ...
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..1275 (rows 1..50)

Crossrefs

Column 1 is A000124(n-1).

Main diagonal is A034856.

Row sums are A002411.

Programs

Mathematica

Table[(n(n-1))/2+2k-1,{n,20},{k,n}]//Flatten (* Harvey P. Dale, Mar 26 2022 *)

Extensions

a(16), a(17) corrected by Georg Fischer, Jul 01 2020

Name changed and terms a(56) and beyond from Andrew Howroyd, Apr 17 2021