OFFSET
7,1
LINKS
Robert Israel, Table of n, a(n) for n = 7..10000
Patric R. J. Östergård and Mattias Svanström, Ternary Constant Weight Codes, The Electronic Journal of Combinatorics, Volume 9 (2002), Research Paper #R41.
Mattias Svanstrom, A lower bound for ternary constant weight codes, IEEE Trans. on Information Theory, Vol. 43 (Sep. 1997), pp. 1630-1632.
Mattias Svanström, A Class of Perfect Ternary Constant-Weight Codes, Designs, Codes and Cryptography, Volume 18, Issue 1-3 (1999), pp. 223-229.
FORMULA
a(n) = ceiling (binomial (n, w) * 2^w / (2*n + 1)) for w = 7.
MAPLE
A:= n -> ceil(binomial(n, 7)*2^7/(2*n+1)):
map(A, [$7 .. 60]); # Robert Israel, Jun 22 2015
MATHEMATICA
a[n_] := Ceiling[Binomial[n, 7] * 2^7 / (2*n + 1)]; Array[a, 40, 7] (* Amiram Eldar, Oct 31 2025 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Mattias Svanstrom (mattias(AT)isy.liu.se)
EXTENSIONS
Formula edited by Robert Israel, Jun 22 2015
STATUS
approved