A077553 Triangle in which the n-th row contains n distinct composite numbers with the least product and has least number of prime divisors. No member of a row is a multiple of another member of the row.

4, 4, 6, 4, 6, 9, 4, 6, 9, 10, 4, 6, 9, 10, 15, 4, 6, 9, 10, 15, 25, 4, 6, 9, 10, 14, 15, 21, 4, 6, 9, 10, 14, 15, 21, 25, 4, 6, 9, 10, 14, 15, 21, 25, 35, 4, 6, 9, 10, 14, 15, 21, 25, 35, 49, 4, 6, 9, 10, 14, 15, 21, 22, 25, 33, 35, 4, 6, 9, 10, 14, 15, 21, 22, 25, 33, 35, 49, 4, 6, 9, 10

Offset

0,1

Comments

If there are two sets of distinct composite numbers satisfying the above condition then the set with lesser product is chosen irrespective of the number of prime divisors. Perhaps the ambiguity may not arise. E.g., row 6 is 4,6,9,10,15,25. This row cannot be extended to get the next row without bringing in another prime because every number divisible by 2,3 or 5 will be a multiple of one of the previous terms. Hence in row 7, prime 7 has to be brought in and then we get a new set of numbers: 4,6,9,10,14,15,21.

Links

Table of n, a(n) for n=0..81.

Example

4;
4,6;
4,6,9;
4,6,9,10;
4,6,9,10,15;
4,6,9,10,15,25;
4,6,9,10,14,15,21;

Crossrefs

Cf. A001358, A005843, A077554, A077555, A087112.

Sequence in context: A365476 A241656 A275161 * A010659 A255014 A131089

Adjacent sequences: A077550 A077551 A077552 * A077554 A077555 A077556

Keyword

nonn,tabl

Author

Amarnath Murthy, Nov 10 2002

Extensions

More terms from Ray Chandler, Aug 21 2003

Status

approved