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 1-3 of 3 results.

A006982 Number of unlabeled distributive lattices on n nodes.

Original entry on oeis.org

1, 1, 1, 1, 2, 3, 5, 8, 15, 26, 47, 82, 151, 269, 494, 891, 1639, 2978, 5483, 10006, 18428, 33749, 62162, 114083, 210189, 386292, 711811, 1309475, 2413144, 4442221, 8186962, 15077454, 27789108, 51193086, 94357143, 173859936, 320462062, 590555664, 1088548290, 2006193418, 3697997558, 6815841849, 12563729268, 23157428823, 42686759863, 78682454720, 145038561665, 267348052028, 492815778109, 908414736485
Offset: 0

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Author

Keywords

References

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

Crossrefs

Extensions

More terms from Jobst Heitzig (heitzig(AT)math.uni-hannover.de), Feb 02 2001. These were computed by the same algorithm that was used to enumerate the posets on 14 elements.

A345734 Number of planar vertically indecomposable distributive lattices with n nodes.

Original entry on oeis.org

1, 1, 0, 1, 0, 1, 0, 2, 1, 4, 2, 9, 6, 21, 18, 48, 50, 114, 135, 277, 358, 681, 935, 1693, 2425, 4235, 6258, 10643, 16085, 26852, 41226, 67921, 105456, 172125, 269375, 436785, 687409, 1109411, 1752966, 2819711, 4468025, 7170045, 11384240, 18238260, 28999047
Offset: 1

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Author

Bianca Newell, Jun 25 2021

Keywords

Crossrefs

Programs

  • PARI
    \\ S is symmetric only, V counts reflections separately.
    S(n)={my(M=matrix(n, sqrtint(n)), v=vector(n)); for(n=1, n, my(s=0); for(k=2, sqrtint(n), s += (k^2==n) + sum(j=2, k-1, v[n-k^2+j^2] - M[n-k^2+j^2, j]); M[n,k]=s); v[n]=s); v}
    V(n)={my(M=matrix(n, n\2), v=vector(n)); for(n=1, n, my(s=0); for(k=2, n\2, s += (2*k==n) + sum(j=2, min(k, n-2*k), v[n+j-2*k] - M[n+j-2*k, j-1]); M[n,k]=s); v[n]=s); v}
    seq(n)={(S(n)+V(n))/2 + vector(n, i, i<=2)} \\ Andrew Howroyd, Jan 24 2023

Extensions

Terms a(23) and beyond from Andrew Howroyd, Jan 24 2023

A368461 a(n) is the number of unlabeled planar modular lattices on n nodes.

Original entry on oeis.org

1, 1, 1, 2, 4, 8, 16, 33, 70, 151, 329, 723, 1601, 3569, 8000, 18015, 40723, 92351, 209997, 478598, 1092856, 2499567, 5724970, 13128115, 30135636, 69238343, 159202607, 366308948, 843338278, 1942591448, 4476714720, 10320774953, 23802355725, 54911686727
Offset: 1

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Author

Jukka Kohonen, Dec 25 2023

Keywords

Crossrefs

Cf. A006981 (modular lattices), A343161 (planar distributive lattices).
Showing 1-3 of 3 results.