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A156870
Number of nondecreasing sequences of 2n positive integers with reciprocals adding up to n (1 <= n).
1
1, 4, 18, 168, 3648, 298165, 159628076
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OFFSET
1,2
COMMENTS
Conjecture:
A156869
(2n + m, n + m) = a(n) if and only if m >= 0.
LINKS
Table of n, a(n) for n=1..7.
EXAMPLE
For n = 2, the a(2) = 4 sequences are (1, 2, 3, 6), (1, 2, 4, 4), (1, 3, 3, 3) and (2, 2, 2, 2) because 1/1 + 1/2 + 1/3 + 1/6 = 1/1 + 1/2 + 1/4 + 1/4 = 1/1 + 1/3 + 1/3 + 1/3 = 1/2 + 1/2 + 1/2 + 1/2 = 2.
CROSSREFS
a(n) =
A156869
(2n, n).
Sequence in context:
A007153
A239839
A367486
*
A240317
A145075
A058924
Adjacent sequences:
A156867
A156868
A156869
*
A156871
A156872
A156873
KEYWORD
more
,
nonn
AUTHOR
Jens Voß
, Feb 17 2009
EXTENSIONS
a(6) from
M. F. Hasler
, Feb 21 2009
a(7) from
Max Alekseyev
, Jan 04 2017
STATUS
approved
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Last modified April 23 12:55 EDT 2024. Contains 371913 sequences. (Running on oeis4.)