

A080511


Triangle whose nth row contains the least set (ordered lexicographically) of n distinct positive integers whose arithmetic mean is an integer.


4



1, 1, 3, 1, 2, 3, 1, 2, 3, 6, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 9, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 12, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 15, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 18, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 21
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,3


COMMENTS

The nth row is {1,2,...,n1,x}, where x=n if n is odd, x=3n/2 if n is even.


LINKS

Table of n, a(n) for n=1..105.


EXAMPLE

Triangle starts:
1;
1, 3;
1, 2, 3;
1, 2, 3, 6;
1, 2, 3, 4, 5;
1, 2, 3, 4, 5, 9;
1, 2, 3, 4, 5, 6, 7;
1, 2, 3, 4, 5, 6, 7, 12;
...


MAPLE

T:= proc(n) $1..n1, `if`(irem(n, 2)=1, n, 3*n/2) end:
seq(T(n), n=1..20); # Alois P. Heinz, Aug 29 2013


MATHEMATICA

row[n_] := Append[Range[n  1], If[OddQ[n], n, 3 n/2]];
Table[row[n], {n, 1, 20}] // Flatten (* JeanFrançois Alcover, May 21 2016 *)


CROSSREFS

Cf. A080512, A008619, A080504, A080508.
Sequence in context: A167373 A079722 A079723 * A132399 A287616 A081485
Adjacent sequences: A080508 A080509 A080510 * A080512 A080513 A080514


KEYWORD

nonn,tabl


AUTHOR

Amarnath Murthy, Mar 20 2003


STATUS

approved



