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A344085
Triangle of squarefree numbers first grouped by greatest prime factor, then sorted by Omega, then in increasing order, read by rows.
6
1, 2, 3, 6, 5, 10, 15, 30, 7, 14, 21, 35, 42, 70, 105, 210, 11, 22, 33, 55, 77, 66, 110, 154, 165, 231, 385, 330, 462, 770, 1155, 2310, 13, 26, 39, 65, 91, 143, 78, 130, 182, 195, 273, 286, 429, 455, 715, 1001, 390, 546, 858, 910, 1365, 1430, 2002, 2145, 3003, 5005, 2730, 4290, 6006, 10010, 15015, 30030
OFFSET
1,2
COMMENTS
Differs from A339195 in having 77 before 66.
EXAMPLE
Triangle begins:
1
2
3 6
5 10 15 30
7 14 21 35 42 70 105 210
MATHEMATICA
nn=4;
GatherBy[SortBy[Select[Range[Times@@Prime/@Range[nn]], SquareFreeQ[#]&&PrimePi[FactorInteger[#][[-1, 1]]]<=nn&], PrimeOmega], FactorInteger[#][[-1, 1]]&]
KEYWORD
nonn,tabf
AUTHOR
Gus Wiseman, May 11 2021
STATUS
approved