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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 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-François 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

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Last modified August 20 07:48 EDT 2019. Contains 326143 sequences. (Running on oeis4.)