A122460 - OEIS

%I #2 Mar 30 2012 18:57:06

%S 4,7,6,10,9,9,13,12,12,12,17,17,15,15,15,22,21,19,20,18,18,25,24,24,

%T 24,22,23,21,31,29,27,27,27,27,25,26,35,33,33,32,30,30,30,30,30,38,38,

%U 37,36,36,35,33,33,35,34,43,42,40,41,40,39,39,38,38,37,39,50,47,45,45,43

%N Triangular array of averages of two odd primes.

%F T(n,k) = (1/2)*(p(k)+p(2n+1-k)) for k=1,2,...,n, where p(1)=3, p(2)=5, ... are the odd primes.

%e First six rows:

%e 4

%e 7 6

%e 10 9 9

%e 13 12 12 12

%e 17 17 15 15 15

%e 22 21 19 20 18 18

%e Row 3 is formed from the first 6 odd primes:

%e 3 5 7 11 13 17 --> (3+17)/2 (5+13)/2 (7+11)/2

%Y Cf. A122459.

%K nonn,tabl

%O 1,1

%A _Clark Kimberling_, Sep 08 2006