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, 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

Offset: 1

Author

Max Barrentine, Oct 02 2015, Nov 03 2015, Nov 05 2015

Keywords

• tabl
• nonn

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.

Examples

			4;
8,   9;
25,  26,  27;
91,  92,  93,  95;
115, 116, 117, 119, 121;
527, 529, 531, 532, 533, 535;
...
		

Links

• Max Barrentine, Table of n, a(n) for n = 1..189

Crossrefs

Subsequence of A002808.

First column is A262042.

Cf. A264482.