

A171876


Mutual solutions to two classification counting problems: binary block codes of wordlength J with N used words; and classifications of N elements by J partitions.


3



1, 1, 1, 1, 1, 3, 3, 1, 1, 4, 6, 19, 27, 50, 56, 1, 1, 5, 10, 47, 131, 472, 1326, 3779, 9013, 19963, 38073, 65664, 98804, 133576, 158658, 1, 1, 6, 16, 103, 497, 3253, 19735, 120843, 681474, 3561696
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OFFSET

0,6


COMMENTS

This connection was conjectured by Robert Munafo, then proved by Andrew Weimholt.
A(n) counts 2colorings of a Jdimensional hypercube with N red vertices and 2^JN black, each edge has at most one red vertex.  Andrew Weimholt, Dec 30 2009
This sequence contains terms of A039754 that are found in A171871/A171872. They occur in blocks of length 2^(J1) as shown here:
1
1,1
1,1,3,3
1,1,4,6,19,27,50,56
1,1,5,10,47,131,472,1326,3779,9013,19963,38073,65664,98804,133576,158658


LINKS

Table of n, a(n) for n=0..41.
Harald Fripertinger, Enumeration of block codes
R. Munafo, Classifications of N Elements


CROSSREFS

Cf. A039754, A171872, A171871, A005646.
Sequence in context: A247646 A133333 A296523 * A133332 A179680 A123562
Adjacent sequences: A171873 A171874 A171875 * A171877 A171878 A171879


KEYWORD

nonn,changed


AUTHOR

Robert Munafo, Jan 21 2010


STATUS

approved



