A063898 Smallest k > 0 such that k + F_n are all primes, where F_n is the n-th Fermat number.
2, 2, 2, 14, 14, 14, 66746, 475424, 12124166, 14899339904
Offset: 0
Examples
For j=3 a(3)=2 because 257+2, 17+2, 5+2, 3+2 are all primes. For j=4 a(4)=14 because 65537+14, 257+14, 17+14, 5+14, 3+14 are all primes.
Crossrefs
Cf. A000215 (Fermat numbers).
Programs
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PARI
okprimep(mink, vecf) = {for (i=1, #vecf, if (! isprime(mink + vecf[i]), return (0));); return (1);} a(n) = {mink = 1; vecf = vector(n+1, i, 2^(2^(i-1)) + 1); while (! okprimep(mink, vecf), mink++); mink;} \\ Michel Marcus, Sep 28 2013
Extensions
a(10) from Donovan Johnson, Oct 12 2008
Comments