A051999 - OEIS

%I #17 Aug 25 2019 15:34:21

%S 4,15,255,5865,170085,5437705,226473065,10380578845,494390700895,

%T 43592479037107

%N Minimal value w such that A051953(w) = w - phi(w) is prime and w has n prime divisors.

%C a(11) <= 2995513256722805. - _Donovan Johnson_, Feb 06 2010

%e a(1)=2^2, a(2)=3*5, a(3)=3*5*17, a(4)=3*5*17*23, a(5)=3*5*17*23*29, a(6)=5437705=5*7*13*17*19*37 with 1,2,3,4,5,6 prime divisors, respectively. The generated primes of form w - phi(w) are as follows: 2, 7, 127, 3049, 91237, 2452721.

%Y Cf. A050530, A051953.

%K nonn,more

%O 1,1

%A _Labos Elemer_, Jan 05 2000

%E a(7)-a(10) from _Donovan Johnson_, Feb 06 2010