The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A187262 Irregular triangle T(n,k), n>=1, 1<=k<=A036234(n), read by rows: T(n,k) is the number of nonempty subsets of {1, 2, ..., n} having <=k pairwise coprime elements. 11
 1, 2, 3, 3, 6, 7, 4, 9, 11, 5, 14, 21, 23, 6, 17, 25, 27, 7, 24, 43, 53, 55, 8, 29, 54, 68, 71, 9, 36, 73, 97, 103, 10, 41, 83, 109, 115, 11, 52, 125, 193, 225, 231, 12, 57, 136, 208, 241, 247, 13, 70, 194, 345, 450, 489, 495, 14, 77, 215, 382, 496, 537, 543 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS T(n,k) = T(n,k-1) for k>A036234(n).  The triangle contains all values of T up to the last element of each row that is different from its predecessor. LINKS Alois P. Heinz, Rows n = 1..200, flattened FORMULA T(n,k) = Sum_{i=1..n,j=1..k} A186972(i,j). T(n,k) = Sum_{j=1..k} A186974(n,j). T(n,k) = Sum_{i=1..n} A186975(i,k). EXAMPLE T(5,3) = 21 because there are 21 nonempty subsets of {1,2,3,4,5} having <=3 pairwise coprime elements: {1}, {2}, {3}, {4}, {5}, {1,2}, {1,3}, {1,4}, {1,5}, {2,3}, {2,5}, {3,4}, {3,5}, {4,5}, {1,2,3}, {1,2,5}, {1,3,4}, {1,3,5}, {1,4,5}, {2,3,5}, {3,4,5}. Irregular Triangle T(n,k) begins:   1;   2,  3;   3,  6,  7;   4,  9, 11;   5, 14, 21, 23;   6, 17, 25, 27;   7, 24, 43, 53, 55; CROSSREFS Columns k=1-10 give: A000027, A187263, A187264, A187265, A187266, A187267, A187268, A187269, A187270, A187271. Rightmost elements of rows give A187106. Cf. A036234, A186972, A186974, A186975. Sequence in context: A159685 A251729 A187763 * A117670 A181695 A322291 Adjacent sequences:  A187259 A187260 A187261 * A187263 A187264 A187265 KEYWORD nonn,tabf AUTHOR Alois P. Heinz, Mar 07 2011 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 21 14:54 EDT 2020. Contains 337272 sequences. (Running on oeis4.)