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 1-10 of 11 results. Next

A006385 Number of unsensed planar maps with n edges.

Original entry on oeis.org

1, 2, 4, 14, 52, 248, 1416, 9172, 66366, 518868, 4301350, 37230364, 333058463, 3057319072, 28656583950, 273298352168, 2645186193457, 25931472185976, 257086490694917, 2574370590192556, 26010904915620261
Offset: 0

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Author

Keywords

Comments

The planar maps considered are connected and may contain loops and parallel edges. - Andrew Howroyd, Jan 13 2025

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • T. R. S. Walsh, personal communication.

Crossrefs

Antidiagonal sums of A277741.
Column k=0 of A379439.
Cf. A000168 (rooted), A006384 (sensed), A006443 (achiral), A006403 (2-connected), A090376.
Cf. A006387 (genus 1), A214814 (genus 2), A214815 (genus 3), A214816.

Formula

a(n) = (A006384(n) + A006443(n))/2. - Andrew Howroyd, Jan 13 2025

Extensions

a(18)-a(19) added by Andrew Howroyd, Jan 13 2025
a(20) added by Andrew Howroyd, Jan 20 2025

A379439 Triangle read by rows: T(n,k) is the number of unsensed combinatorial maps with n edges and genus k, 0 <= k <= floor(n/2).

Original entry on oeis.org

1, 2, 4, 1, 14, 6, 52, 40, 4, 248, 320, 76, 1416, 2946, 1395, 82, 9172, 29364, 24950, 4348, 66366, 309558, 427336, 160050, 7258, 518868, 3365108, 6987100, 4696504, 688976, 4301350, 37246245, 109761827, 118353618, 37466297, 1491629, 37230364, 416751008, 1668376886, 2675297588, 1512650776, 195728778
Offset: 0

Views

Author

Andrew Howroyd, Jan 16 2025

Keywords

Examples

			Triangle begins:
  n\k     [0]      [1]      [2]      [3]     [4]
  [0]      1;
  [1]      2;
  [2]      4,       1;
  [3]     14,       6;
  [4]     52,      40,       4;
  [5]    248,     320,      76;
  [6]   1416,    2946,    1395,      82;
  [7]   9172,   29364,   24950,    4348;
  [8]  66366,  309558,  427336,  160050,   7258;
  [9] 518868, 3365108, 6987100, 4696504, 688976;
		

Crossrefs

Row sums are A214816.
Cf. A269919 (rooted), A379438 (sensed), A380234 (achiral), A380235.

Formula

T(n,k) = (A379438(n,k) + A380234(n,k))/2.

A214816 Number of unsensed combinatorial maps with n edges on an orientable surface of any genus.

Original entry on oeis.org

1, 2, 5, 20, 96, 644, 5839, 67834, 970568, 16256556, 308620966, 6506035400, 150358570914, 3775903806928, 102348067516576, 2977979542305736, 92579723269733557, 3062602106878957610, 107418879166917701583, 3981908920500346885116, 155550644128029095714786
Offset: 0

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Author

N. J. A. Sloane, Jul 31 2012

Keywords

Crossrefs

Row sums of A379439.
Cf. A006385, A006387, A170946 (sensed), A170947 (achiral), A170948 (chiral pairs), A214814, A214815, A297880, A297881, A348798, A348800, A348801.

Formula

a(n) = (A170946(n) + A170947(n)) / 2. [Breda d'Azevedo, Mednykh & Nedela, Corollary 4.7] - Andrey Zabolotskiy, Jun 06 2024

Extensions

a(12)-a(18) from Andrey Zabolotskiy, Jun 06 2024
a(19) onwards from Andrew Howroyd, Jan 27 2025

A104595 Number of unrooted maps with n edges of (orientable) genus 2.

Original entry on oeis.org

4, 106, 2382, 46680, 830848, 13804864, 218353000, 3328822880, 49325772812, 714586880940, 10164338225482, 142403410942816, 1969831979334086, 26954132420126920, 365393525753591368, 4913176199287631232, 65593569635906036912, 870192550284377429780, 11479539192932030062066
Offset: 4

Views

Author

Valery A. Liskovets, Mar 22 2005

Keywords

Crossrefs

Column k=2 of A379438.
Cf. A006301 (rooted), A214814 (unsensed).

A006387 Number of unsensed genus 1 maps with n edges.

Original entry on oeis.org

0, 0, 1, 6, 40, 320, 2946, 29364, 309558, 3365108, 37246245, 416751008, 4696232371, 53186743416, 604690121555, 6896534910612, 78867385697513, 904046279771682, 10384916465797240, 119522063788612992, 1378014272286250059
Offset: 0

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Author

Keywords

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Column k=1 of A379439.
Cf. A006300 (rooted), A006385 (planar), A006386 (sensed), A214814, A214815, A214816.

Extensions

a(12)-a(20) from Evgeniy Krasko, Sep 17 2017

A214815 Number of unsensed genus 3 maps with n edges.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 82, 4348, 160050, 4696504, 118353618, 2675297588, 55758114082, 1091344752470, 20318440463052, 363171011546210, 6275111078422480, 105369657960443204, 1726590417107274316, 27699670730854989616, 436246336648672487876
Offset: 0

Views

Author

N. J. A. Sloane, Jul 31 2012

Keywords

Crossrefs

Column k=3 of A379439.
Cf. A104742 (rooted), A104596 (sensed).

Extensions

More terms from Evgeniy Krasko, Sep 17 2017

A297880 Number of unsensed genus 4 maps with n edges.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 7258, 688976, 37466297, 1512650776, 50355225387, 1461269893538, 38236656513725, 922552326544030, 20847359639841664, 446290728182323620, 9129236228868478458, 179639607187998993180, 3418366706444416598777
Offset: 0

Views

Author

Evgeniy Krasko, Jan 07 2018

Keywords

Crossrefs

Column k=4 of A379439.
Cf. A215402 (rooted), A215019 (sensed).

Extensions

a(20) added by Andrew Howroyd, Jan 20 2025

A348798 a(n) = number of unsensed genus 6 maps with n edges.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 506855279, 84930743344, 7601322881752, 482475325333252, 24347701836204379, 1038820801135250668, 38928478953655850016, 1314623638623845390906, 40749347642026348171659
Offset: 0

Views

Author

Michael De Vlieger, Nov 01 2021

Keywords

Crossrefs

Column k=6 of A379439.
Cf. A238356 (rooted), A239919 (sensed).

A297881 Number of unsensed genus 5 maps with n edges.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1491629, 195728778, 14019733828, 724646387874, 30220873171570, 1079253898643492, 34231899372185491, 988157793188200998, 26412878913430197293, 662133032168309300424, 15719783014093104131694
Offset: 0

Views

Author

Evgeniy Krasko, Jan 07 2018

Keywords

Crossrefs

Column k=5 of A379439.
Cf. A238355 (rooted), A239918 (sensed).

A348800 a(n) = number of unsensed genus 7 maps with n edges.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 254118439668, 52148049818864, 5634797561708385, 426497331688178676, 25388940147173859412, 1265623233919838264624, 54940200059090328012148
Offset: 0

Views

Author

Michael De Vlieger, Nov 01 2021

Keywords

Crossrefs

Column k=7 of A379439.
Cf. A238357 (rooted), A239921 (sensed).
Showing 1-10 of 11 results. Next