login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A217563 Irregular triangular array read by rows. T(n,k)  is the number of weakly connected relations on n labeled nodes with k arcs. (n>=0, 0<=k<=n^2) 0
1, 1, 1, 0, 2, 5, 4, 1, 0, 0, 12, 56, 111, 123, 84, 36, 9, 1, 0, 0, 0, 128, 944, 3264, 7096, 10936, 12687, 11400, 8004, 4368, 1820, 560, 120, 16, 1, 0, 0, 0, 0, 2000, 21104, 109400, 373920, 950725, 1915405, 3168880, 4394760, 5169230, 5188390, 4454000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Row sums = A062738.

LINKS

Table of n, a(n) for n=0..49.

FORMULA

E.g.f.: Log[Sum_{n>=0} (1+y)^(n^2) x^n/n!] + 1

EXAMPLE

1,

1, 1,

0, 2, 5, 4, 1,

0, 0, 12, 56, 111, 123, 84, 36, 9, 1,

0, 0, 0, 128, 944, 3264, 7096, 10936, 12687, 11400, 8004, 4368, 1820, 560, 120, 16, 1

MATHEMATICA

nn=6; s=Sum[(1+y)^(n^2) x^n/n!, {n, 0, nn}]; Range[0, nn]! CoefficientList[Series[ Log[s]+1, {x, 0, nn}], {x, y}] //Grid

CROSSREFS

Cf. A062735.

Sequence in context: A324057 A106315 A285295 * A254881 A100946 A200019

Adjacent sequences:  A217560 A217561 A217562 * A217564 A217565 A217566

KEYWORD

nonn,tabf

AUTHOR

Geoffrey Critzer, Oct 07 2012

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 December 2 05:09 EST 2020. Contains 338865 sequences. (Running on oeis4.)