

A063897


a(n) is the least k such that k  A000215(j), j=0..n, are all primes.


1




OFFSET

0,1


COMMENTS

Is this sequence finite?
The prime ktuples conjecture implies that the sequence is infinite.  Robert Israel, Jul 11 2016


LINKS

Table of n, a(n) for n=0..6.


EXAMPLE

For j=0 a(0)=5 because 53 is prime.
For j=1 a(1)=8 because 85, 83 are all primes.
For j=2 a(2)=22 because 2217, 225, 223 are all primes.
For j=3 a(3)=274 because 274257, 27417, 2745, 2743 are all primes.


MAPLE

f:= proc(n) local r, j, good;
for r from 2^(2^n)+4 by 2 do
good:= true;
for j from 0 to n do
if not isprime(r  2^(2^j)1) then good:= false; break fi
od;
if good then return(r) fi
od
end proc:
f(0):= 5:
map(f, [$0..5]); # Robert Israel, Jul 11 2016


PROG

(PARI) okprime(mink, vecf) = {for (i = 1, #vecf, if (! isprime(mink  vecf[i]), return (0)); ); return (1); }
a(n) = {mink = 2^(2^n) + 2; vecf = vector(n+1, i, 2^(2^(i1)) + 1); while (! okprime(mink, vecf), mink++); mink; } \\ Michel Marcus, Sep 28 2013


CROSSREFS

Cf. A000215.
Sequence in context: A120041 A120042 A120043 * A092733 A116884 A192651
Adjacent sequences: A063894 A063895 A063896 * A063898 A063899 A063900


KEYWORD

hard,more,nonn


AUTHOR

Felice Russo, Aug 29 2001


EXTENSIONS

18446744073810262144 from Thomas Baruchel, Oct 21 2003


STATUS

approved



