

A225055


Irregular triangle which lists the three positions of 2*n1 in A060819 in row n.


3



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
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


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*n1: 2*n1 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.


LINKS

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


FORMULA

T(n,1) = 2*n1. T(n,2) = 4*n2. T(n,3) = 8*n4.


EXAMPLE

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;


MATHEMATICA

numberOfTriplets = 19; A060819 = Table[n/GCD[n, 4], {n, 1, 8*numberOfTriplets}]; Table[Position[A060819, 2*n1], {n, 1, numberOfTriplets}] // Flatten (* JeanFrançois Alcover, Apr 30 2013 *)


CROSSREFS

Cf. A147587. A042968.
Sequence in context: A134561 A258046 A334384 * A120947 A222600 A046793
Adjacent sequences: A225052 A225053 A225054 * A225056 A225057 A225058


KEYWORD

nonn,tabf,easy


AUTHOR

Paul Curtz, Apr 26 2013


STATUS

approved



