%N Largest value held in any register at the end of a halting computation by an n-instruction register Minski machine.
%C We start with initially empty registers and include exactly one Halt instruction. Analogous to the Busy Beaver function, Sigma, for Turing Machines.
%C n<=5 are proved. 5<n<=9 are good lower bounds.
%D Tibor Rado, On Noncomputable Functions, Bell System Technical Journal, vol. 41, # 3, 877-884, May 1963.
%e E.g. B(3) is of the form:
%e 1: A+ -> 2
%e 2: A+ -> 3
%e 3: Halt
%e Halting with B(3)=2
%Y Cf. A028444.
%A Rick J. Griffiths (rjg42(AT)cam.ac.uk), Apr 20 2003