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 1-5 of 5 results.

A294685 Triangle read by rows: T(n,k) is the number of non-isomorphic colorings of a toroidal n X k grid using exactly three colors under translational symmetry, 1 <= k <= n.

Original entry on oeis.org

0, 0, 9, 2, 91, 2022, 9, 738, 43315, 2679246, 30, 5613, 950062, 174184755, 33887517990, 91, 43404, 21480921, 11765865678, 6862930841141, 4169289730628814, 258, 338259, 497812638, 816999710223, 1429469771994078, 2605213713043722909, 4883659745750360600262, 729, 2679228, 11765822365, 57906482267826, 303941554100145501
Offset: 1

Views

Author

Marko Riedel, Nov 06 2017

Keywords

Comments

Colors are not being permuted, i.e., Power Group Enumeration does not apply here.

Examples

			Triangle begins:
   0;
   0,     9;
   2,    91,     2022;
   9,   738,    43315,     2679246;
  30,  5613,   950062,   174184755,   33887517990;
  91, 43404, 21480921, 11765865678, 6862930841141, 4169289730628814;
  ...
		

References

  • F. Harary and E. Palmer, Graphical Enumeration, Academic Press, 1973.

Crossrefs

Main diagonal is A376823.

Programs

  • PARI
    T(n,m)=6*sumdiv(n, d, sumdiv(m, e, eulerphi(d) * eulerphi(e) * stirling(n*m/lcm(d,e), 3, 2) ))/(n*m) \\ Andrew Howroyd, Oct 05 2024

Formula

T(n,k) = (Q!/(n*k))*(Sum_{d|n} Sum_{f|k} phi(d) phi(f) S(gcd(d,f)*(n/d)*(k/f), Q)) with Q=3 and S(n,k) Stirling numbers of the second kind.
T(n,k) = A184284(n,k) - 3*A184271(n,k) + 3. - Andrew Howroyd, Oct 05 2024

A376822 Number of colorings of a toroidal n X n grid using exactly two colors under translational symmetry.

Original entry on oeis.org

0, 5, 62, 4154, 1342206, 1908897150, 11488774559742, 288230376353050814, 29850020237398264483838, 12676506002282327791964489726, 21970710674130840874443091905462270, 154866286100907105149651981766316633972734, 4427744605404865645682169434028029029963535286270
Offset: 1

Views

Author

Andrew Howroyd, Oct 05 2024

Keywords

Crossrefs

Main diagonal of A294684.
Cf. A179043, A376747 (colors permutable), A376823, A376824, A376825.

Formula

a(n) = A179043(n) - 2.

A376824 Number of colorings of a toroidal n X n grid using exactly four colors under translational symmetry.

Original entry on oeis.org

0, 6, 20720, 257706024, 44900438149488, 131160169581733489616, 6467585568566200114362823920, 5316911768534424725926923896066891424, 72172920340122292837562997014593985220649867760, 16069380442569287654590340470284256047904187412954757496784
Offset: 1

Views

Author

Andrew Howroyd, Oct 05 2024

Keywords

Crossrefs

Main diagonal of A294686.
Cf. A179043, A184272, A184278, A376749 (colors permutable), A376822, A376823, A376825.

Formula

a(n) = A184272(n) - 4*A184278(n) + 6*A179043(n) - 4.

A376825 Number of colorings of a toroidal n X n grid using exactly five colors under translational symmetry.

Original entry on oeis.org

0, 0, 92680, 8221452750, 11696087875731720, 403564024914127655401650, 362489465982555360136794113733480, 8470302887983624205463771824482291388274750, 5106052803042976484591492152983188808422646355702792360, 78886090441754278328274880503253722147584506163456748572863233329010
Offset: 1

Views

Author

Andrew Howroyd, Oct 05 2024

Keywords

Crossrefs

Main diagonal of A294687.

A376748 Number of non-isomorphic colorings of a toroidal n X n grid using exactly three swappable colors.

Original entry on oeis.org

0, 3, 345, 447156, 5647919665, 694881637942816, 813943290958393433377, 8941884948534360647405572800, 912400181570021638669407666368774097, 858962534553352212055863239761275173880606456, 7425662396340624836407113113710889289196975262054947345, 587417576454184723055270940786413231085263155884260701824558793960
Offset: 1

Views

Author

Marko Riedel, Oct 03 2024

Keywords

References

  • F. Harary and E. Palmer, Graphical Enumeration, Academic Press, 1973.

Crossrefs

Main diagonal of A294792.

Formula

a(n) = (1/(n^2*3!))*(Sum_{sigma in S_3} Sum_{d|n} Sum_{f|n} phi(d) phi(f) [[forall j_l(sigma) > 0 : l|lcm(d,f) ]] P(gcd(d,f)*(n/d)*(n/f), sigma)) where P(F, sigma) = F! [z^F] Product_{l=1..3} (exp(lz)-1)^j_l(sigma). The notation j_l(sigma) is from the Harary text and gives the number of cycles of length l in the permutation sigma. [[.]] is an Iverson bracket.
Showing 1-5 of 5 results.