cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A193130 Numbers of spanning trees of the cocktail party graphs.

Original entry on oeis.org

0, 4, 384, 82944, 32768000, 20736000000, 19271206305792, 24759631762948096, 42071440246337175552, 91403961001574400000000, 247248735803801600000000000, 815050629127324260701847945216, 3217014140995401936351315753959424
Offset: 1

Views

Author

Eric W. Weisstein, Jul 16 2011

Keywords

Comments

Number of trees on 2n labeled vertices containing no edges from a prescribed perfect matching. - Joel B. Lewis, Jun 20 2013

References

  • Dragoš M. Cvetković, Michael Doob, Horst Sachs, Spectra of Graphs: Theory and Application, Academic Press, 1980.

Crossrefs

Cf. A091159 (up to isomorphism).

Formula

a(n) = n^(n-2) * (n-1)^n * 4^(n-1). [See "Spectra of graphs", p. 217; also observed by Joel B. Lewis, Jun 20 2013] - Andrey Zabolotskiy, Mar 18 2021

A319587 The number of distinct solid nets of the six convex regular 4D-polytopes in the order of their 3D-cell count.

Original entry on oeis.org

3, 261, 110912, 17895697067018274
Offset: 1

Views

Author

Frank M Jackson, Sep 23 2018

Keywords

Comments

These values have been taken from the Buekenhout (1998) paper (see link). During the unfolding of these solid nets along their common face, the possibility of any overlapping is ignored.
This finite sequence is fully determined but a(5) and a(6) are too large to be displayed in data. See formulas below to calculate these terms.

Crossrefs

Programs

  • Mathematica
    {3, (82944+12*16+24*8+4*2304+6*128+12*96+12*192+12*288)/(2^7*3), 2^5(2^7*3^3+1+3^2), 6(2^19*5688888889+347), 2^7*5^2*7^3(2^114*3^78*5^20*7^33+2^47*3^18*5^2*7^12*53^5*2311^3+239^2*3931^2), 2^188*3^102*5^20*7^36*11^48*23^48*29^30}

Formula

a(1) = 3;
a(2) = (82944 + 12*16 + 24*8 + 4*2304 + 6*128 + 12*96 + 12*192 + 12*288)/(2^7 * 3) = 261;
a(3) = 2^5*(2^7 * 3^3 + 1 + 3^2) = 110912;
a(4) = 6*(2^19 * 5688888889 + 347) = 17895697067018274;
a(5) = 2^7 * 5^2 * 7^3 * (2^114 * 3^78 * 5^20 * 7^33 + 2^47 * 3^18 * 5^2 * 7^12 * 53^5 * 2311^3 + 239^2 * 3931^2);
a(6) = 2^188 * 3^102 * 5^20 * 7^36 * 11^48 * 23^48 * 29^30.
Showing 1-2 of 2 results.