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 A089924 Number of plane partitions of n with 3 or more columns. 6
 0, 0, 1, 3, 8, 19, 41, 85, 167, 319, 588, 1066, 1880, 3272, 5588, 9431, 15686, 25841, 42070, 67926, 108634, 172467, 271643, 425109, 660756, 1021170, 1568905, 2398059, 3646437, 5519025, 8314623, 12473538, 18634748, 27731820, 41113453, 60735830, 89411503, 131193675 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS Because of symmetry of the 3-dimensional-Ferrers plots, this sequence also counts the plane partitions with 3 or more rows and the plane partitions with maximal element >= 3 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..5000 W. Meeussen, PlanePartitions (Mathematica program, personal web site). EXAMPLE a(4)=3: 1111 111 211 .... 1.. ... MAPLE b:= proc(n, k) option remember; `if`(n=0, 1, add(add(min(d, k) *d, d=numtheory[divisors](j))*b(n-j, k), j=1..n)/n) end: a:= n-> b(n, infinity)-b(n, 2): seq(a(n), n=1..50); # Alois P. Heinz, Sep 24 2018 MATHEMATICA (* planepartitions[] : see link *); Table[Count[planepartitions[n], q_ /; Length[First[q]] >= 3], {n, 12}] CROSSREFS Cf. A000219, A000991, A091357. Sequence in context: A182818 A095846 A153732 * A293947 A178457 A072916 Adjacent sequences: A089921 A089922 A089923 * A089925 A089926 A089927 KEYWORD nonn AUTHOR Wouter Meeussen, Jan 11 2004 EXTENSIONS a(21)-a(27) from Vaclav Kotesovec, May 05 2018 a(28)-a(38) from Alois P. Heinz, Sep 24 2018 STATUS approved

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Last modified July 20 20:50 EDT 2024. Contains 374459 sequences. (Running on oeis4.)