A214442 - OEIS

%I #9 Jul 23 2012 14:55:09

%S 3,18,3318,39193162,943016093,390502539,3

%N Arithmetic mean of next a(n) > 1 successive odd primes is prime.

%C Two or more primes in the arithmetic mean.

%C Corresponding prime arithmetic means: 5, 43, 14639, 369687067, 11370090223, 27055575571, 31756143437

%e (3+5+7)/3 is prime, so a(1)=3; next (11+13+...+73+79)/18=43 is prime, so a(2)=18.

%t n = 1; Table[n++; s = Prime[n]; num = 1; While[num == 1 || ! PrimeQ[s/num], n++; num++; s = s + Prime[n]]; num, {3}] (* _T. D. Noe_, Jul 23 2012 *)

%Y Cf. A000040, A073684.

%K nonn,more

%O 1,1

%A _Alex Ratushnyak_, Jul 18 2012