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!)
 A261987 Triangle read by rows: row n lists the set of n coprime composite numbers that minimizes the difference between first and last terms, and then minimizes the average of the terms. 4
 4, 8, 9, 25, 26, 27, 91, 92, 93, 95, 115, 116, 117, 119, 121, 527, 529, 531, 532, 533, 535, 527, 529, 531, 533, 535, 536, 539, 1331, 1333, 1334, 1337, 1339, 1341, 1343, 1345, 1331, 1333, 1334, 1337, 1339, 1341, 1343, 1345, 1349 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The minimal set of the (k+n)th row is determined by the minimal k-tuple coprime to the n-th primorial, where every prime <= to the n-th prime must be a factor of some number in the set. E.g., the sixth row must consist of numbers congruent to 5, 7, 11 and 13 mod 6, as well as one term with a factor of 2 and another with a factor of 3. In cases where multiple k-tuples satisfy the definition, the lexicographically earliest solution is chosen. LINKS Max Barrentine, Table of n, a(n) for n = 1..189 EXAMPLE 4; 8,   9; 25,  26,  27; 91,  92,  93,  95; 115, 116, 117, 119, 121; 527, 529, 531, 532, 533, 535; ... CROSSREFS Subsequence of A002808. First column is A262042. Cf. A264482. Sequence in context: A035326 A180865 A063907 * A158340 A259183 A056166 Adjacent sequences:  A261984 A261985 A261986 * A261988 A261989 A261990 KEYWORD tabl,nonn AUTHOR Max Barrentine, Oct 02 2015, Nov 03 2015, Nov 05 2015 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 19 18:53 EDT 2020. Contains 337181 sequences. (Running on oeis4.)