This site is supported by donations to The OEIS Foundation.

 Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS". Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.