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 1-7 of 7 results.

A034382 Number of labeled Abelian groups of order n.

Original entry on oeis.org

1, 2, 3, 16, 30, 360, 840, 15360, 68040, 907200, 3991680, 159667200, 518918400, 14529715200, 163459296000, 4250979532800, 22230464256000, 1200445069824000, 6758061133824000, 405483668029440000
Offset: 1

Views

Author

Keywords

Crossrefs

Formula

a(n) = A058162(n) * n.
a(n) = Sum n!/|Aut(G)|, where the sum is taken over the different products G of cyclic groups with |G|=n. Formula for |Aut(G)| is given by Hillar and Rhea (2007). Another formula is given by Sugarknri (2019).

Extensions

a(16) corrected by Max Alekseyev, Sep 12 2019

A058160 Triangle read by rows: T(n,k) is the number of labeled commutative monoids of order n with k idempotents and a fixed identity.

Original entry on oeis.org

1, 1, 1, 1, 6, 2, 4, 45, 36, 9, 6, 408, 648, 348, 76, 60, 7195, 13500, 11790, 5280, 1065, 120, 200016, 369930, 425280, 293640, 118890, 22566, 1920, 13811077, 14716716, 18035745, 16347660, 9953265, 3750516, 674611, 7560, 3405271616, 1024787568, 971651856, 999666920, 794967600, 445001424, 157962168, 27019896
Offset: 1

Views

Author

Christian G. Bower, Nov 14 2000

Keywords

Examples

			Triangle begins:
   1;
   1,    1;,
   1,    6,     2;
   4,   45,    36,     9;
   6,  408,   648,   348,   76;
  60, 7195, 13500, 11790, 5280, 1065;
  ...
		

Crossrefs

Row sums give A058156.
Column 1: A058162.
Main diagonal A058164.
Cf. A058142 (isomorphism classes), A058158, A058159.

Formula

T(n, k) = A058159(n, k)/n.

Extensions

Terms a(30) and beyond from Andrew Howroyd, Feb 15 2022

A055512 Lattices with n labeled elements.

Original entry on oeis.org

1, 1, 2, 6, 36, 380, 6390, 157962, 5396888, 243179064, 13938711210, 987858368750, 84613071940452, 8597251494954564, 1020353444641839854, 139627532137612581090, 21788453795572514675760, 3840596246648027262079472, 758435490711709577216754642
Offset: 0

Views

Author

Jobst Heitzig (heitzig(AT)math.uni-hannover.de), Jul 03 2000

Keywords

Crossrefs

Cf. A006966, A001035. Main diagonal of A058159.

A058142 Triangle read by rows: number of commutative monoids of order n with k idempotents.

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 2, 9, 6, 2, 1, 26, 30, 16, 5, 1, 98, 142, 111, 54, 15, 1, 455, 718, 713, 482, 215, 53, 3, 4018, 4277, 4637, 3919, 2414, 996, 222, 2, 101910, 36124, 32937, 31308, 24047, 13758, 5294, 1078, 1, 10054303, 708355, 290278, 260758, 229411, 164216, 88178, 31867, 5994
Offset: 1

Views

Author

Christian G. Bower, Nov 14 2000

Keywords

Examples

			Triangle begins:
  1;
  1,  1;
  1,  3,   1;
  2,  9,   6,   2;
  1, 26,  30,  16, 5;
  1, 98, 142, 111, 54, 15;
  ...
		

Crossrefs

Row sums give A058131.
Main diagonal: A006966.
Columns 1..2: A000688, A058143.

Extensions

a(30)-a(55) from Andrew Howroyd, Feb 15 2022

A058155 Number of labeled commutative monoids of order n.

Original entry on oeis.org

1, 4, 27, 376, 7430, 233340, 10013094, 618332080, 70437029472, 39048511536720
Offset: 1

Views

Author

Christian G. Bower, Nov 14 2000, corrected Dec 05 2003

Keywords

Crossrefs

Cf. A058156.
Row sums of A058159.

Formula

a(n) = A058156(n)*n.

Extensions

a(8)-a(9) from Alex Meiburg, Oct 20 2021
a(10) from Andrew Howroyd, Feb 15 2022

A058157 Triangle read by rows: T(n,k) is the number of labeled monoids of order n with k idempotents.

Original entry on oeis.org

1, 2, 2, 3, 18, 12, 16, 180, 288, 140, 30, 2640, 6540, 8380, 3020, 480, 119610, 238200, 421020, 372360, 100362, 840, 25196052, 13786290, 26803000, 36174600, 22822674, 4768624, 22080, 48687313640, 2254725312, 2358499080, 3849768160, 3859581096, 1826525120, 305498328
Offset: 1

Views

Author

Christian G. Bower, Nov 14 2000

Keywords

Examples

			Triangle begins:
   1;
   2,    2;
   3,   18,   12;
  16,  180,  288,  140;
  30, 2640, 6540, 8380, 3020;
  ...
		

Crossrefs

Row sums give A058153.
Column 1: A034383.
Main diagonal is A351731.
Cf. A058137 (isomorphism classes), A058158, A058159 (commutative), A058166.

Formula

T(n,k) = A058158(n,k)*n.

Extensions

a(30)-a(36) from Andrew Howroyd, Feb 15 2022

A173488 Partial sums of A055512.

Original entry on oeis.org

1, 2, 4, 10, 46, 426, 6816, 164778, 5561666, 248740730, 14187451940, 1002045820690, 85615117761142, 8682866612715706, 1029036311254555560, 140656568448867136650, 21929110364021381812410, 3862525357012048643891882, 762298016068721625860646524
Offset: 0

Views

Author

Jonathan Vos Post, Feb 19 2010

Keywords

Comments

Partial sums of the number of lattices with n labeled elements. After a(0) = 1, always even, hence the only prime in the partial sum is 2. The subsequence of semiprimes begins 4, 10, 46.

Crossrefs

Cf. A055512, A006966, A001035, Main diagonal of A058159.

Programs

Formula

a(n) = Sum_{i=0..n} A055512(i).

Extensions

a(17)-a(18) from Jean-François Alcover, Jan 02 2020
Showing 1-7 of 7 results.