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!)
A238951 The number of arcs from odd to even level vertices in divisor lattice D(n). 4
0, 0, 0, 1, 0, 2, 0, 1, 1, 2, 0, 3, 0, 2, 2, 2, 0, 3, 0, 3, 2, 2, 0, 5, 1, 2, 1, 3, 0, 6, 0, 2, 2, 2, 2, 6, 0, 2, 2, 5, 0, 6, 0, 3, 3, 2, 0, 6, 1, 3, 2, 3, 0, 5, 2, 5, 2, 2, 0, 10, 0, 2, 3, 3, 2, 6, 0, 3, 2, 6, 0, 8, 0, 2, 3, 3, 2, 6, 0, 6, 2, 2, 0, 10, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

R. J. Mathar, Table of n, a(n) for n = 1..1000

S.-H. Cha, E. G. DuCasse, and L. V. Quintas, Graph Invariants Based on the Divides Relation and Ordered by Prime Signatures, arXiv:1405.5283 [math.NT], 2014 (see 12th line in Table 1).

FORMULA

a(n) = A062799(n) - A238950(n) = floor(A062799(n)/2). [Cha eqs. (2.34), (2.37)]

MAPLE

read("transforms"):

omega := [seq(A001221(n), n=1..1000)] ;

ones := [seq(1, n=1..1000)] ;

a062799 := DIRICHLET(ones, omega) ;

for n from 1 do

    a238951 := floor(op(n, a062799)/2) ;

    printf("%d %d\n", n, a238951) ;

end do: # R. J. Mathar, May 28 2017

CROSSREFS

Cf. A056924, A062799, A238950.

Sequence in context: A329747 A304455 A345354 * A071466 A155041 A334296

Adjacent sequences:  A238948 A238949 A238950 * A238952 A238953 A238954

KEYWORD

nonn

AUTHOR

Sung-Hyuk Cha, Mar 07 2014

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 17 13:48 EDT 2022. Contains 353746 sequences. (Running on oeis4.)