OFFSET
1,2
EXAMPLE
Corner of McGarvey's array (from A007062):
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
2 1 4 3 6 5 8 7 10 9 12 11 14 13 16 15 18 17 20 19
4 1 2 5 6 3 10 7 8 11 12 9 16 13 14 17 18 15 22 19
5 2 1 4 7 10 3 6 9 12 11 8 17 14 13 16 19 22 15 18
7 4 1 2 5 12 8 6 3 10 13 14 17 8 11 18 15 22 19 16
12 5 2 1 4 7 14 13 10 3 6 8 22 15 18 11 8 17 24 23
14 7 4 1 2 5 12 15 22 8 6 3 10 13 20 23 24 17 8 11
15 12 5 2 1 4 7 14 23 20 13 10 3 6 8 22 25 28 31 18
(Column 3) = (3,4,2,1,1,2,4,5,7,12,23,...) in which the numbers 1,2,4 occur more than once.
MATHEMATICA
a = Range[x = 40000]; rows = Table[a = Flatten[Map[Reverse, Partition[a, n]]], {n,
NestWhile[# + 1 &, 1, (x = # Floor[x/#]) > 0 &] - 1}];
Flatten[Table[{Length[Select[SortBy[Tally[Map[#[[col]] &, rows]], #[[2]] &], #[[2]] > 1 &]]}, {col, 100}]] (* Peter J. C. Moses, May 01 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, May 04 2023
STATUS
approved