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 A320436 Irregular triangle read by rows where T(n,k) is the number of pairwise coprime k-subsets of {1,...,n}, 1 <= k <= A036234(n), where a single number is not considered to be pairwise coprime unless it is equal to 1. 3
 1, 1, 1, 1, 3, 1, 1, 5, 2, 1, 9, 7, 2, 1, 11, 8, 2, 1, 17, 19, 10, 2, 1, 21, 25, 14, 3, 1, 27, 37, 24, 6, 1, 31, 42, 26, 6, 1, 41, 73, 68, 32, 6, 1, 45, 79, 72, 33, 6, 1, 57, 124, 151, 105, 39, 6, 1, 63, 138, 167, 114, 41, 6, 1, 71, 159, 192, 128, 44, 6, 1, 79 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 LINKS EXAMPLE Triangle begins:    1    1   1    1   3   1    1   5   2    1   9   7   2    1  11   8   2    1  17  19  10   2    1  21  25  14   3    1  27  37  24   6    1  31  42  26   6    1  41  73  68  32   6    1  45  79  72  33   6    1  57 124 151 105  39   6    1  63 138 167 114  41   6    1  71 159 192 128  44   6    1  79 183 228 157  56   8 MATHEMATICA Table[Length[Select[Subsets[Range[n], {k}], CoprimeQ@@#&]], {n, 16}, {k, PrimePi[n]+1}] CROSSREFS Except for the k = 1 column, same as A186974. Row sums are A320426. Second column is A015614. Cf. A051424, A084422, A085945, A187106, A276187, A320423, A320430, A320435. Sequence in context: A245369 A076334 A014475 * A135228 A021325 A174609 Adjacent sequences:  A320433 A320434 A320435 * A320437 A320438 A320439 KEYWORD nonn,tabf AUTHOR Gus Wiseman, Jan 08 2019 STATUS approved

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Last modified April 5 03:15 EDT 2020. Contains 333238 sequences. (Running on oeis4.)