login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A173311 Partial sums of A000112. 0
1, 2, 4, 9, 25, 88, 406, 2451, 19450, 202681, 2769965, 49519392, 1154411138, 34978238590, 1373171398361, 69648249299517, 4552778914494604 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Partial sums of number of partially ordered sets ("posets") with n unlabeled elements. It is a law of small numbers example that this sequence, through the largest known terms, has three consecutive squares (4, 9, 25) and no primes other than 2.

LINKS

Table of n, a(n) for n=0..16.

FORMULA

a(n) = Sum_{i=0..n} A000112(i).

MATHEMATICA

Cases[Import["https://oeis.org/A000112/b000112.txt", "Table"], {_, _}][[All, 2]] // Accumulate (* Jean-Fran├žois Alcover, Jan 01 2020 *)

CROSSREFS

Cf. A000112, A000798 (labeled topologies), A001035 (labeled posets), A001930 (unlabeled topologies), A006057, A079263, A079265.

Sequence in context: A192801 A270954 A173496 * A127055 A124835 A125799

Adjacent sequences:  A173308 A173309 A173310 * A173312 A173313 A173314

KEYWORD

nonn,hard,more

AUTHOR

Jonathan Vos Post, Feb 16 2010

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 21 00:46 EST 2022. Contains 350473 sequences. (Running on oeis4.)