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A156871 Number of nondecreasing sequences of n positive integers with reciprocals adding up to an integer. 4
1, 2, 5, 20, 170, 3650, 298132, 159632503 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
a(n) = A156869(n, 1) + ... + A156869(n, n).
EXAMPLE
For n = 3, the A156871(3) = 5 sequences are (1, 1, 1), (1, 2, 2), (2, 3, 6), (2, 4, 4) and (3, 3, 3) because 1/1 + 1/1 + 1/1 = 3, 1/1 + 1/2 + 1/2 = 2 and 1/2 + 1/3 + 1/6 = 1/2 + 1/4 + 1/4 = 1/3 + 1/3 + 1/3 = 1.
CROSSREFS
Sequence in context: A159320 A184730 A181076 * A058109 A005331 A261005
KEYWORD
more,nonn
AUTHOR
Jens Voß, Feb 17 2009
EXTENSIONS
a(7), a(8) from Max Alekseyev, Jul 27 2009
STATUS
approved

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Last modified March 28 16:58 EDT 2024. Contains 371254 sequences. (Running on oeis4.)