A331640 Number of binary matrices with n columns and any number of distinct nonzero rows with 2 ones in every column.

1, 0, 6, 120, 6174, 449520, 49686726, 7455901320, 1479839874414, 373573957133280, 117097298726892246, 44596327028174342520, 20287402287658565190654, 10864410524883717498300240, 6765647366010527963979060966, 4847736403559133115838948559720

Offset

0,3

Links

Andrew Howroyd, Table of n, a(n) for n = 0..200

Formula

a(n) ~ n!^2 * c * d^n / sqrt(n), where d = 3.2910168844935423141034... and c = 0.1950905980407344575730... - Vaclav Kotesovec, Feb 10 2026

Example

The a(2) = 6 matrices are:
   [1 1]  [1 1]  [1 0]  [1 0]  [0 1]  [0 1]
   [1 0]  [0 1]  [1 1]  [0 1]  [1 1]  [1 0]
   [0 1]  [1 0]  [0 1]  [1 1]  [1 0]  [1 1]

Crossrefs

Row n=2 of A331567.

Cf. A331641.

Sequence in context: A093910 A002370 A012846 * A012641 A012795 A054479

Adjacent sequences: A331637 A331638 A331639 * A331641 A331642 A331643

Keyword

nonn

Author

Andrew Howroyd, Jan 23 2020

Status

approved