

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
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OFFSET

1,1


COMMENTS

The minimal set of the (k+n)th row is determined by the minimal ktuple coprime to the nth primorial, where every prime <= to the nth 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 ktuples 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



