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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

Table of n, a(n) for n=1..8.

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

Cf. A002966, A156869, A280517, A280518.

Sequence in context: A159320 A184730 A181076 * A058109 A005331 A261005

Adjacent sequences:  A156868 A156869 A156870 * A156872 A156873 A156874

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 November 20 04:05 EST 2017. Contains 294959 sequences.