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A085782 Numbers that can be written as a product of triangular numbers. 7
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 (list; graph; refs; listen; history; text; internal format)
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: A111359 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

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Last modified May 21 06:36 EDT 2022. Contains 353889 sequences. (Running on oeis4.)