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A048139 Number of planar partitions of n, when partitions that are rotations of each other (when regarded as 3-D objects) are counted only once. 1
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; text; internal format)
OFFSET

1,3

COMMENTS

Plane partitions seen as 3-dimensional-objects can have a threefold symmetry axis.

LINKS

Table of n, a(n) for n=1..37.

EXAMPLE

n=3 gives 2 forms: {{3}}={{1,1,1}}={{1},{1},{1}} and {{2,1}}={{1,1},{1}}={{2},{1}}.

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 A240951 A280373

Adjacent sequences:  A048136 A048137 A048138 * A048140 A048141 A048142

KEYWORD

nonn

AUTHOR

Wouter Meeussen

EXTENSIONS

Edited by N. J. A. Sloane, Oct 26 2008 at the suggestion of R. J. Mathar.

STATUS

approved

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Last modified June 23 16:45 EDT 2017. Contains 288666 sequences.