A128233 - OEIS

%I #4 Jul 30 2020 16:02:08

%S 4,8,12,21,27,38,43,53,69,79,97,110,117,129,147,168,172,199,212,220,

%T 240,257,275,303,324,333,347,354,365,418,435,455,468,504,514,538,565,

%U 579,602,621,634,672,682,699,708,754,816,830,838,852,869,882,924,939,966

%N Average of p(n) and p(p(n)), where p(k) is the k-th prime.

%e a(4)=12 because p(4)=7 and p(7)=17.

%p a:=n->(ithprime(n)+ithprime(ithprime(n)))/2: seq(a(n),n=2..70);

%t Table[Mean[{Prime[n],Prime[Prime[n]]}],{n,2,60}] (* _Harvey P. Dale_, Jul 30 2020 *)

%Y Cf. A128234.

%K nonn

%O 2,1

%A _Emeric Deutsch_, Feb 20 2007