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A080511 Triangle whose n-th 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 n-th row is {1,2,...,n-1,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..n-1, `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 (* Jean-Fran├žois Alcover, May 21 2016 *)

CROSSREFS

Cf. A080512, A008619, A080504, A080508.

Sequence in context: A167373 A079722 A079723 * A132399 A081485 A100337

Adjacent sequences:  A080508 A080509 A080510 * A080512 A080513 A080514

KEYWORD

nonn,tabl

AUTHOR

Amarnath Murthy, Mar 20 2003

STATUS

approved

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Last modified March 26 06:49 EDT 2017. Contains 284111 sequences.