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A048139
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Number of planar partitions of n, when partitions that are rotations of each other (when regarded as 3-D objects) are counted only once.
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1
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1, 1, 2, 5, 8, 16, 30, 54, 94, 168, 287, 493, 831, 1391, 2293, 3769, 6114, 9867, 15782, 25098, 39598, 62165, 96935, 150398, 232021, 356261, 544220, 827758, 1253222, 1889655, 2837455, 4244505, 6324993, 9392009, 13897056, 20494991, 30126628
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Plane partitions seen as 3-dimensional-objects can have a threefold symmetry axis.
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EXAMPLE
| n=3 gives 2 forms: {{3}}={{1,1,1}}={{1},{1},{1}} and {{2,1}}={{1,1},{1}}={{2},{1}}.
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CROSSREFS
| Equals Cs + 2 C1 + 2 C3 + C3v, Cs=A000784, C1=A000785, C3=A048142, C3v=A048141. Cf. A000219, A005987.
Or, equals (2*A048141+A000219+4*A048142)/3.
Sequence in context: A026530 A032254 A048237 * A071085 A055236 A103041
Adjacent sequences: A048136 A048137 A048138 * A048140 A048141 A048142
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KEYWORD
| nonn
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AUTHOR
| Wouter Meeussen (wouter.meeussen(AT)pandora.be)
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Oct 26 2008 at the suggestion of R. J. Mathar.
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