OFFSET
1,1
COMMENTS
a(11) itself is the primary source of interest for this particular sequence, since already at a(4) we have the first value permitting concatenation of a 7th prime. A219677 contains the sequence where successors are placed in sequence to the left rather than the right.
LINKS
C. Rivera, PrimePuzzles.Net, Puzzle 708 Find sets of k consecutive primes such that ...
EXAMPLE
The 72-digit prime 10000069939910000699417100000699439100000699453100000699517100000699543 is the concatenation of 6 successive primes, and deletion from the right results in a shorter prime for all 5 steps. So, 100000699399 is one of the terms of this sequence, a(11).
PROG
(PARI) /* Output is a vector of 6 consecutive primes for each element of the sequence, the 1st of these primes. */
{
\\ This program first checks for consistency mod 3\\
p=[5, 7, 11, 13, 17, 19]; e=[10, 100, 100, 100, 100];
while(1,
if((p[1]+p[2])%3, f=1; for(i=2, 5,
if((p[i]+p[i+1])%3, f=0; break()));
if(f, P=p[1]*e[1]+p[2]; if(ispseudoprime(P),
for(i=2, 5, P*=e[i]; P+=p[i+1]; if(ispseudoprime(P)==0,
f=0; break())); if(f, print(p)))));
for(i=1, 5, p[i]=p[i+1]); p(6)=nextprime(p[6]+1);
for(i=1, 4, e[i]=e[i+1]); if(p[6]>e[5], e[5]*=10))
}
(PARI) is(n)=my(p=n); if(!ispseudoprime(p), return(0)); for(i=1, 5, n=eval(Str(n, p=nextprime(p+1))); if(!ispseudoprime(n), return(0))); 1 \\ Charles R Greathouse IV, Oct 06 2013
CROSSREFS
KEYWORD
nonn,base
AUTHOR
James G. Merickel, Nov 17 2012
EXTENSIONS
Terms missing (5 of 11) added by James G. Merickel, Jul 20 2013
Typo in a(9) fixed by James G. Merickel, Oct 06 2013
a(12)-a(15) from Charles R Greathouse IV, Oct 10 2013
STATUS
approved