A085782 Numbers that can be written as a product of triangular numbers.

0, 1, 3, 6, 9, 10, 15, 18, 21, 27, 28, 30, 36, 45, 54, 55, 60, 63, 66, 78, 81, 84, 90, 91, 100, 105, 108, 120, 126, 135, 136, 150, 153, 162, 165, 168, 171, 180, 189, 190, 198, 210, 216, 225, 231, 234, 243, 252, 253, 270, 273, 276, 280, 300, 315, 324, 325, 330, 351

Offset

1,3

Comments

These are the numbers that appear at least once in A007425 (the number of ordered factorizations of n as n = r*s*t). - Matthew Vandermast, Jul 26 2003

Contains A085780 as a subsequence (exactly 2 factors); 27,54,81,... are the first elements in the complement. - M. F. Hasler, Apr 03 2008

The number of r-orthotopes of any size contained in a n1*n2*...*nr r-orthotope, where a(n)=t(n1)*t(n2)*...*t(nr) and t(k)=A000217(k). - Dimitri Boscainos, Aug 27 2015

Links

David A. Corneth, Table of n, a(n) for n = 1..10000

Example

54 = 6*3*3 = t(3)*t(2)*t(2).

Crossrefs

Cf. A000217, A007425, A085780, A334115.

Sequence in context: A359352 A274428 A344158 * A085780 A166047 A310141

Adjacent sequences: A085779 A085780 A085781 * A085783 A085784 A085785

Keyword

nonn

Author

Jon Perry, Jul 23 2003

Extensions

More terms from Max Alekseyev and Jon E. Schoenfield, Sep 04 2009

Status

approved