A079833 - OEIS

%I #5 Dec 05 2013 19:55:59

%S 2,7,5,7,7,71,71,71,71,71,13,71,19,71,19,71,19,71,71,71,71,71,71,71,

%T 71,71,31,71,31,71,37,71,37,71,43,59,43,71,43,811,43,71,59,71,59,71,

%U 811,811,811,71,59,811,59,811,59,71,61,811,61,163,73,811,73,71,73,811,73

%N Define f(n) = n + tau(n), then a(n) = smallest prime of the type f(f(f...f(n)))).

%e a(6) = 71 as f(6) = 10, f(10) = 14, f(14) = 18, f(18) = 24, f(24) = 32, f(32) = 38, f(38) = 42, f(42) = 50, f(50) = 56, f(56) = 64, f(64) = 64 +7 = 71.

%o (PARI) { a(n) = local(k,m); k=1; m=n; while(1, m=m+numdiv(m); if(isprime(m),return(m)); k++ ) } (Alekseyev)

%Y Cf. A079834.

%K nonn

%O 1,1

%A _Amarnath Murthy_, Feb 12 2003

%E More terms from _Max Alekseyev_, Apr 19 2005