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%I #40 Nov 18 2018 07:51:59
%S 13,17,131,4127,18191,10131071,1524287,362147483647,
%T 152305843009213693951,58618970019642690137449562111,
%U 57162259276829213363391578010288127,55170141183460469231731687303715884105727
%N Prefixing digits to Mersenne primes to obtain larger primes.
%C The smallest prefixing digits for the Mersenne primes are given in A209385. - _Gilbert Mozzo_, Mar 07 2012
%C The next term a(13) has 160 decimal digits. - _Andrew Howroyd_, Nov 17 2018
%H Henri Lifchitz and Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/prptop.php">PRP Top Records</a>
%F Mersenne prime + n*10^D with D = number of digits of the Mersenne prime.
%e For Mersenne4: -1 + 2^7 + 4*10^3 = 4127 which is prime.
%o (PARI)
%o ppfx(n)={my(w=10^(1+logint(n,10)), k=n+w); while(!ispseudoprime(k), k+=w); k}
%o { for(n=1, 100, my(p=1<<prime(n)-1); if(ispseudoprime(p), print1(ppfx(p), ", "))) } \\ _Andrew Howroyd_, Nov 17 2018
%Y Cf. A000668, A209385.
%K nonn,base
%O 1,1
%A _Gilbert Mozzo_, Dec 12 2011
%E a(7)-a(9) added by _Gilbert Mozzo_, Mar 07 2012
%E a(10)-a(12) from _Andrew Howroyd_, Nov 17 2018
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