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 A091356 Number of planar partitions of n with exactly 2 rows. 5
 1, 2, 5, 9, 18, 30, 53, 85, 139, 215, 336, 504, 760, 1115, 1635, 2351, 3375, 4770, 6725, 9368, 13006, 17885, 24510, 33319, 45139, 60743, 81457, 108610, 144334, 190844, 251542, 330082, 431825, 562710, 731154, 946644, 1222305, 1573155, 2019471 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 LINKS Alois P. Heinz, Table of n, a(n) for n = 2..10000 FORMULA a(n) = A000990(n) - A000041(n). 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, 2)-b(n, 1): seq(a(n), n=2..50);  # Alois P. Heinz, Oct 02 2018 CROSSREFS Column 2 of A091355. Cf. A000219, A091357-A091360. Sequence in context: A184353 A019135 A069957 * A107705 A278690 A288578 Adjacent sequences:  A091353 A091354 A091355 * A091357 A091358 A091359 KEYWORD nonn AUTHOR Christian G. Bower, Jan 02 2004 STATUS approved

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Last modified October 21 08:47 EDT 2019. Contains 328292 sequences. (Running on oeis4.)