A101445 - OEIS

%I #7 Mar 13 2015 05:01:06

%S 2,3,40087,251737

%N Numbers n such that n is the largest prime factor of 1 + prime(n).

%C No more terms below the (10^7)-th prime, i.e., 179424673. - _Robert G. Wilson v_, Jan 21 2005

%e 3 = the largest factor of 1 + prime(3) = 6, so 3 belongs to the sequence.

%t Select[ Prime[ Range[ 10^7]], Transpose[ FactorInteger[ Prime[ # ] + 1]][[1, -1]] == # &]

%K nonn

%O 1,1

%A _Joseph L. Pe_, Jan 18 2005