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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

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Last modified September 19 18:53 EDT 2020. Contains 337181 sequences. (Running on oeis4.)