A225055 Irregular triangle which lists the three positions of 2*n-1 in A060819 in row n.

1, 2, 4, 3, 6, 12, 5, 10, 20, 7, 14, 28, 9, 18, 36, 11, 22, 44, 13, 26, 52, 15, 30, 60, 17, 34, 68, 19, 38, 76, 21, 42, 84, 23, 46, 92, 25, 50, 100, 27, 54, 108, 29, 58, 116, 31, 62, 124, 33, 66, 132, 35, 70, 140, 37, 74, 148

Offset: 1

Author

Paul Curtz, Apr 26 2013

Keywords

• nonn
• tabf
• easy

Comments

There are no multiples of 8 in the triangle.

A047592 contains a sorted list of all elements of the triangle.

The triangle is a member of a family of triangles with parameter k that list the k positions of 2*n-1: 2*n-1 in A000027 (k=1), A043547 the k=2 positions in A026741, the triangle 1,2,4,8; 3,6,12,24;... with the k=4 positions in A106609, or the triangle 1,2,4,8,16; 3,6,12,24,48;... with the k=5 positions in A106617.

Examples

			1, 2, 4;  # 1 at A060819(1), A060819(2) and A060819(4)
3, 6, 12;  # 3 at A060819(3), A060819(6) and A060819(12)
5, 10, 20;
7, 14, 28;
9, 18, 36;
11, 22, 44;
13, 26, 52;
15, 30, 60;
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A147587. A042968.

Programs

Mathematica

numberOfTriplets = 19; A060819 = Table[n/GCD[n, 4], {n, 1, 8*numberOfTriplets}]; Table[Position[A060819, 2*n-1], {n, 1, numberOfTriplets}] // Flatten (* Jean-François Alcover, Apr 30 2013 *)

Formula

T(n,1) = 2*n-1. T(n,2) = 4*n-2. T(n,3) = 8*n-4.