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A180282 Number of arrangements of n indistinguishable balls in n boxes with the maximum number of balls in any box equal to 2 2
2, 6, 18, 50, 140, 392, 1106, 3138, 8952, 25652, 73788, 212940, 616226, 1787606, 5196626, 15134930, 44152808, 128996852, 377379368, 1105350728, 3241135526, 9513228122, 27948336380, 82176836300, 241813226150, 712070156202 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

R. H. Hardin, Table of n, a(n) for n=2..59

FORMULA

a(n)=sum{j=1..n}binomial(n,j)*binomial(n-j,j)=2*A097861(n)

CROSSREFS

Column 2 of A180281

A097861

Sequence in context: A062026 A048495 A089380 * A081154 A002900 A199770

Adjacent sequences:  A180279 A180280 A180281 * A180283 A180284 A180285

KEYWORD

nonn

AUTHOR

R. H. Hardin Aug 24 2010

STATUS

approved

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Last modified June 19 05:40 EDT 2013. Contains 226390 sequences.