OFFSET
1,1
COMMENTS
See A123206 for primes of the form x^y-y^x with x,y>1. If y=1 is allowed, any prime p is obtained for x=p+1; this motivates the "y+1" in the exponent of the present sequence.
y=0 would give "Primes of the form x", so y>0 is required. y=1 gives x^2-1 = (x-1)*(x+1) which is only prime for x=2. - Jens Kruse Andersen, Aug 23 2014
LINKS
Jens Kruse Andersen, Table of n, a(n) for n = 1..59
J. S. Gerasimov, x^(y + 1) - y^x, SeqFan list, Aug 18, 2014
PROG
(PARI) a=[]; for(S=1, 199, for(x=1, S-1, ispseudoprime(p=x^(1+y=S-x)-y^x)&&a=concat(a, p))); vecsort(a) \\ The list calculated this way is probably not complete up to the last terms. E.g., a 46 digit prime is found for x=3, y=97 after three larger terms for smaller S=x+y.
(PARI) m=300; a=[]; for(x=1, m+5, for(y=1, m+5, p=x^(y+1)-y^x; if(p<2^m && ispseudoprime(p), a=concat(a, p)))); a=vecsort(a) \\ Compute all terms below 2^m. Jens Kruse Andersen, Aug 23 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, Aug 19 2014
STATUS
approved