A069179 Least number X such that for each k in (0 to n-1), 2^k*X-1 and 2^k*X+1 are primes. That is, there are N twin primes, each the "double" of the previous.

4, 6, 211050, 253680, 41887255410, 73768891456260

Offset

1,1

Comments

a(6)=73768891456260 might be called a(6.5), since 64*a(6)+1 is prime. But 64*a(6)-1 is 167*1021*44533*621769, alas.

Links

Table of n, a(n) for n=1..6.

Example

a(3) = 211050 because 1*a(3)-1, 1*a(3)+1, 2*a(3)-1, 2*a(3)+1, 4*a(3)-1 and 4*a(3)+1 are all prime.

Crossrefs

Equals A068635 + 1.

Sequence in context: A077305 A146294 A133982 * A336764 A058377 A023961

Adjacent sequences: A069176 A069177 A069178 * A069180 A069181 A069182

Keyword

nonn

Author

Don Reble, Apr 09 2002

Status

approved