A087749 Primes p such that 6^p - 5^p is composite.
3, 7, 17, 19, 29, 31, 37, 41, 43, 47, 53, 59, 67, 71, 73, 79, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281
Offset: 1
Keywords
Crossrefs
Cf. A005062.
Programs
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Mathematica
Select[Prime[Range[60]],!PrimeQ[6^#-5^#]&] (* Harvey P. Dale, Apr 26 2011 *)
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PARI
apmb(a,b,n) = { forprime(x=2,n, y=a^x-b^x; if(!ispseudoprime(y), print1(x","); ) ) }
Extensions
Corrected by Andrew S. Plewe, Apr 24 2007 (all the terms were wrong)
Checked by Ray Chandler, Apr 25 2007