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 1-4 of 4 results.

A198761 Number of hopping sequences in four-colored rooted trees with n nodes, starting and ending with the same "initial state" from all of the (two-colored) rooted trees in A198760. See comments.

Original entry on oeis.org

2, 20, 648, 45472, 5644880, 1099056000, 310007943616, 119777421416192
Offset: 2

Views

Author

N. J. A. Sloane, Oct 29 2011

Keywords

Comments

Compared to A225823, both node colors of the initial states are mobile on the tree (Hubbard model). - Eva Kalinowski, Jul 30 2013

References

  • G. Gruber, Entwicklung einer graphbasierten Methode zur Analyse von Hüpfsequenzen auf Butcherbäumen und deren Implementierung in Haskell, Diploma thesis, Marburg, 2011
  • M. Paech, E. Kalinowski, W. Apel, G. Gruber, R. Loogen, and E. Jeckelmann, Ground-state energy and beyond: High-accuracy results for the Hubbard model on the Bethe lattice in the strong-coupling limit, DPG Spring Meeting, Berlin, TT 45.91 (2012)

Crossrefs

Extensions

Terms a(8) and a(9) added by Martin Paech, Apr 16 2012

A136794 Number of unlabeled marked rooted trees with n nodes.

Original entry on oeis.org

2, 8, 52, 376, 2998, 25256, 222128, 2013680, 18691522, 176743160, 1696546848, 16488151400, 161919802562, 1604274741608, 16016845623764, 160977882238968, 1627406260427490, 16537733701226936
Offset: 1

Views

Author

Christian G. Bower, Jan 21 2008

Keywords

Comments

A marked rooted tree is a rooted tree where each node and edge is marked as + or -.

References

  • F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, p. 293 (4.1.60).

Crossrefs

Cf. A136795 (tree version), A136796 (labeled version).

Formula

a(n) = A136793(n)/2 = A052763(n)*2.

A225823 Number of hopping sequences in four-colored rooted trees with n nodes, starting and ending with the same "initial state" from all of the (two-colored) rooted trees in A198760. Compared to A198761, only one node color of the initial states is mobile on the tree (Falicov-Kimball model).

Original entry on oeis.org

1, 4, 54, 1568, 80680, 6510624, 761286848, 121944722176, 25668462562560
Offset: 2

Views

Author

Eva Kalinowski, Jul 30 2013

Keywords

References

  • G. Gruber, Entwicklung einer graphbasierten Methode zur Analyse von Hüpfsequenzen auf Butcherbäumen und deren Implementierung in Haskell, Diploma thesis, Marburg, 2011
  • M. Paech, E. Kalinowski, W. Apel, G. Gruber, R. Loogen, and E. Jeckelmann, Ground-state energy and beyond: High-accuracy results for the Hubbard model on the Bethe lattice in the strong-coupling limit, DPG Spring Meeting, Berlin, TT 45.91 (2012)

Crossrefs

Extensions

Term a(10) added by Martin Paech, Sep 02 2013, calculated on a HP Integrity Superdome 2-32s by courtesy of Hewlett-Packard Development Company, L.P.

A242354 Number T(n,k) of four-colored rooted trees of order n and structure k; triangle T(n,k), n>=1, 1<=k<=A000081(n), read by rows.

Original entry on oeis.org

4, 16, 64, 40, 256, 160, 256, 80, 1024, 640, 1024, 320, 1024, 640, 544, 640, 140, 4096, 2560, 4096, 1280, 4096, 2560, 2176, 2560, 560, 4096, 2560, 4096, 1280, 4096, 2560, 2560, 1600, 2176, 1280, 224, 16384, 10240, 16384, 5120, 16384, 10240, 8704, 10240, 2240
Offset: 1

Views

Author

Martin Paech, May 16 2014

Keywords

Comments

The underlying partitions of n-1 (cf. A000041) for the construction of the trees with n nodes are generated in descending order, the elements within a partition are sorted in ascending order, e.g.,
n = 1
{0} |-> () |-> 10_2
n = 2
{1} |-> (()) |-> 1100_2
n = 3
{2} > {1, 1} |-> ((())) > (()()) |-> 111000_2 > 110100_2
n = 4
{3} > {1, 2} > {1, 1, 1} |-> (((()))) > ((()())) > (()(())) > (()()()) |-> 11110000_2 > 11101000_2 > 11011000_2 > 11010100_2
The decimal equivalents of the binary encoded rooted trees in row n are the descending ordered elements of row n in A216648.

Examples

			Let {h, u, d, p} be a set of four colors, corresponding to the four possible "states" of each tree node (lattice site) in the underlying physical problem, namely its occupation with no electron (hole), with one up-spin electron, with one down-spin electron, or with one up-spin and one down-spin electron (pair). (We consider each rooted tree as a cutout of the Bethe lattice in infinite dimensions.) Then for
n = 1 with A000081(1) = 1
  h(), u(), d(), p() are the 4 four-colored trees of the first and only structure k = 1 (sum is 4 = A136793(1)); for
n = 2 with A000081(2) = 1
  h(h()), h(u()), h(d()), h(p()),
  u(h()), u(u()), u(d()), u(p()),
  d(h()), d(u()), d(d()), d(p()),
  p(h()), p(u()), p(d()), p(p()) are the 16 four-colored trees of the first and only structure k = 1 (sum is 16 = A136793(2)); for
n = 3 with A000081(3) = 2
  h(h(h())), h(h(u())), h(h(d())), h(h(p())),
  h(u(h())), ...
                              ..., p(d(p())),
  p(p(h())), p(p(u())), p(p(d())), p(p(p())) are the 64 four-colored trees of the structure k = 1 and
  h(h()h()), h(h()u()), h(h()d()), h(h()p()),
  h(u()u()), h(u()d()), h(u()p()),
  h(d()d()), h(d()p()),
  h(p()p()),
  ...,
  p(h()h()), p(h()u()), p(h()d()), p(h()p()),
  p(u()u()), p(u()d()), p(u()p()),
  p(d()d()), p(d()p()),
  p(p()p()) are the 40 four-colored trees of the structure k = 2 (sum is 104 = A136793(3)).
Triangle T(n,k) begins:
4;
16;
64, 40;
256, 160, 256, 80;
1024, 640, 1024, 320, 1024, 640, 544, 640, 140;
		

References

  • G. Gruber, Entwicklung einer graphbasierten Methode zur Analyse von Hüpfsequenzen auf Butcherbäumen und deren Implementierung in Haskell, Diploma thesis, Marburg, 2011
  • Eva Kalinowski, Mott-Hubbard-Isolator in hoher Dimension, Dissertation, Marburg: Fachbereich Physik der Philipps-Universität, 2002.

Crossrefs

Row sums give A136793.
Row length is A000081.
Total number of elements up to and including row n is A087803.
Showing 1-4 of 4 results.