A238778 - OEIS

%I #13 Jan 24 2022 10:01:17

%S 2,3,8,15,12,21,32,36,40,55,72,65,56,90,64,119,144,57,120,168,132,161,

%T 240,200,156,270,168,203,360,155,320,396,136,350,432,333,380,546,320,

%U 369,672,387,352,810,368,423,672,294,600,816,520,583,864,660,784

%N Sum of all primes p such that 2n - p is also a prime.

%C Sum of n-th row in triangle A171637.

%H Reinhard Zumkeller, <a href="/A238778/b238778.txt">Table of n, a(n) for n = 2..10000</a>

%F a(n) = A008472(A238711(n)).

%F a(n) mod 2 = A010051(n).

%F a(n) = n*A035026(n). - _Robert G. Wilson v_, Apr 28 2018

%o (Haskell)

%o a238778 n = sum $ filter ((== 1) . a010051') $

%o    map (2 * n -) $ takeWhile (<= 2 * n) a000040_list

%o (PARI) a(n) = my(s=0); forprime(p=2, 2*n, if(isprime(2*n-p), s+=p)); s; \\ _Michel Marcus_, Jan 24 2022

%Y Cf. A008472, A238711.

%Y Cf. A010051, A035026, A171637

%K nonn

%O 2,1

%A _Reinhard Zumkeller_, Mar 06 2014