OFFSET
1,1
COMMENTS
Let b(n) be the sequence giving the values of the primes p corresponding to a(n). b(1)-b(4) are 3, 3, 3, 5 (cf. (ii) and (iv) in Scott, Styer, 2004).
Any other pair (p, d) must be of the form (A001220(i), d) for some i > 2 (cf. Corollary to Theorem 2 in Scott, Styer, 2004).
LINKS
R. Scott and R. Styer, On p^x - q^y = c and related three term exponential Diophantine equations with prime bases, Journal of Number Theory, Vol. 105, No. 2 (2004), 212-234.
EXAMPLE
Two solutions (x, y) of the Diophantine equation 5^x - 2^y = -3 are (1, 3) and (3, 7), so -3 is a term of the sequence.
CROSSREFS
KEYWORD
sign,hard,more,bref
AUTHOR
Felix Fröhlich, Oct 31 2016
STATUS
approved