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.

A380630 Number of matrices with n columns, any number of distinct rows and entries in 0..2 and without an all zero row up to permutations of rows and columns.

Original entry on oeis.org

1, 4, 144, 11250688, 50371911404609819639808, 58894902159279477652776826941706227937004584169809397602591562463707136
Offset: 0

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Author

Andrew Howroyd, Feb 19 2025

Keywords

Comments

The matrices can be regarded as sets of n-tuples. Equivalence is up to simultaneous permutations of the tuples.
Another interpretation as the number of non-isomorphic formulas in conjunctive normal form is described in A380610.

Crossrefs

Row sums of A380610.

Programs

  • PARI
    \\ Fix, permcount defined in A380610.
    a(n)={my(s=0); forpart(q=n, s+=permcount(q)*Fix(q, 1)); s/n!/2}