OFFSET
1,7
COMMENTS
A numerical semigroup is a set of natural numbers closed under addition. Its Frobenius number is the largest number not in it.
A generator is extraneous if it can be generated by other generators.
LINKS
J. L. Davison, On the linear Diophantine problem of Frobenius numbers, J. Number Theory 48 (1994), p353-363.
J. C. Rosales, P. A. Garcia-Sanchez and J. I. Garcia-Garcia, Every positive integer is the Frobenius number of a numerical semigroup with three generators, Math. Scand. 94 (2004), no. 1, 5-12.
J. C. Rosales and M. B. Branco, Irreducible numerical semigroups, Pacific J. Math. 209 (2003), no. 1, 131-143.
EXAMPLE
a(7)=3 because are three such semigroups with Frobenius number 7. Their complements (and a generating triple) are {1,2,3,7} (4,5,6); {1,2,4,5,7} (3,8,10); {1,2,3,6,7} (4,5,11).
CROSSREFS
KEYWORD
nonn
AUTHOR
Kaye A. Archer (godchaser_2(AT)hotmail.com), May 06 2004
EXTENSIONS
Edited by Don Reble, Apr 26 2007
STATUS
approved