A132169 Irregular triangle read by rows. A141616(n)/4.

2, 3, 6, 4, 8, 5, 12, 10, 6, 15, 12, 7, 20, 18, 14, 8, 24, 21, 16, 9, 30, 28, 24, 18, 10, 35, 32, 27, 20, 11, 42, 40, 36, 30, 22, 12, 48, 45, 40, 33, 24, 13, 56, 54, 50, 44, 36, 26, 14, 63, 60, 55, 48, 39, 28, 15, 72, 70, 66, 60, 52, 42, 30, 16

Offset

0,1

Comments

From Paul Curtz, Apr 14 2016: (Start)

Row sums: A023856.

Even rows: A120070.

Odd rows:

2,

6, 4,

12, 10, 6,

etc.

Divided by 2:

1,

3, 2,

6, 5, 3,

10, 9, 7, 4,

15, 14, 12, 9, 5,

etc.

This is A049777. Or positive A049780.

Also A271668 without the first column and bordered by the natural numbers as main diagonal.

(End)

Links

Table of n, a(n) for n=0..63.

Example

Irregular triangle:
2,
3,
6,   4,
8,   5,
12, 10, 6,
15, 12, 7,
20, 18, 14,  8,
24, 21, 16,  9,
30, 28, 24, 18, 10,
35, 32, 27, 20, 11,
etc.

Mathematica

(Table[n^2 - k^2, {n, 3, 18}, {k, n}] /. m_ /; Or[OddQ@ m, m == 0] -> Nothing)/4 // Flatten (* Michael De Vlieger, Apr 14 2016 *)

Crossrefs

Cf. A023856, A049777, A049780, A052938, A120070, A131723, A141616, A168230, A198442, A271668.

Sequence in context: A258078 A036552 A257987 * A273666 A302023 A112975

Adjacent sequences: A132166 A132167 A132168 * A132170 A132171 A132172

Keyword

nonn,tabf

Author

Paul Curtz, Aug 26 2008

Extensions

Edited by Charles R Greathouse IV, Nov 11 2009

Status

approved