OFFSET
1,1
COMMENTS
These rational numbers represent a FRACTRAN program capable of calculating any computable function.
If, when started at c*2^(2^k), the program stops at 2^(2^m), then c encodes the computable function f_c, and f_c(k) = m, where c, k and m are nonnegative integers.
In the linked work Conway lists some values of c (which he calls "catalog numbers") encoding various simple functions, including the (extremely large) value of c for computing the k-th digit in the decimal expansion of Pi.
LINKS
J. H. Conway, "FRACTRAN: A Simple Universal Programming Language for Arithmetic", in T. M. Cover and B. Gopinath, eds, Open Problems in Communication and Computation, Springer, New York, NY, 1987, pp. 4-26.
J. H. Conway, "FRACTRAN: A Simple Universal Programming Language for Arithmetic", in J. C. Lagarias, ed., The Ultimate Challenge: The 3x+1 Problem, American Mathematical Society, 2010, pp. 249-264.
Wikipedia, FRACTRAN.
CROSSREFS
KEYWORD
nonn,frac,fini,full
AUTHOR
Paolo Xausa, Jan 10 2022
STATUS
approved