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Conference rusure::math

Title:Mathematics at DEC
Moderator:RUSURE::EDP
Created:Mon Feb 03 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2083
Total number of notes:14613

516.0. "The Frobenius Problem" by CLT::GILBERT (Juggler of Noterdom) Tue Jun 17 1986 03:51

Suppose that a country wishes to issue stamps in a limited number of
denominations a1, a2, ..., ak.  What is the largest value which cannot
be achieved using only those denominations, and how many values cannot
be achieved?
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516.1LATOUR::JMUNZERTue Jun 17 1986 15:569
    Peter:
    
    Why is it called the Frobenius Problem?
    
    Are there restrictions on a1, a2, ..., ak?  If k = 2, a1 = 5, and
    a2 = 10, are the values that cannot be achieved = {1,2,3,4,6,7,8,9,11,
    12,...}, or something else?
    
    John
516.2CLT::GILBERTJuggler of NoterdomTue Jun 17 1986 19:3413
This problem is named after the German mathmematician Frobenius, apparently
because of a comment by Brauer that "Frobenius mentioned it occasionally in
his lectures".

For the problem to make sense, assume that gcd(a1,a2,...,ak) = 1, and that
all a1,a2,...,ak are > 1.  Also, assume that a1,a2,...,ak are independent:
that none can be represented as a linear combination with nonnegative integer
coefficients of the others.

For example g(5,7) = 23, and g(5,7,9) = 13.

[ The problem is shown to be related to Shellsort in this month's issue of
  the Journal of Algorithms.  A bibliography can also be found there. ]
516.3but what's next?LATOUR::JMUNZERMon Jun 23 1986 21:151
    g(a1, a2) = a1 * a2 - a1 - a2