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

1,2

Links

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

Example

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;
  ...

Mathematica

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

Crossrefs

Column 1 is A000124(n-1).

Main diagonal is A034856.

Row sums are A002411.

Sequence in context: A376638 A135692 A089003 * A221952 A007843 A239826

Adjacent sequences: A132115 A132116 A132117 * A132119 A132120 A132121

Keyword

nonn,easy,tabl

Author

Gary W. Adamson, Aug 10 2007

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

Status

approved