A305126 Number of ways to express n^3 as average of two primes p1 < p2.

0, 2, 5, 3, 9, 19, 16, 22, 48, 37, 44, 89, 55, 80, 188, 76, 100, 220, 124, 191, 382, 199, 223, 419, 326, 296, 561, 373, 368, 983, 400, 435, 1001, 514, 872, 1145, 630, 689, 1483, 956, 794, 1981, 926, 1075, 2624, 1085, 1122, 2340, 1442, 1700

Offset: 1

Author

Hugo Pfoertner, May 26 2018

Keywords

• nonn

Links

• Hugo Pfoertner, Table of n, a(n) for n = 1..500

Crossrefs

Cf. A002375, A305125.

Programs

Magma

A305126 := func; [A305126(n^3):n in[1..70]]; // Vincenzo Librandi, May 26 2018

Mathematica

f[n_]:=Length[Select[2 n - Prime[Range[2, PrimePi[n]]], PrimeQ]]; Table[f[n^3], {n, 60}] (* Vincenzo Librandi, May 26 2018 *)

PARI

for (n=1,50,k=0;n3=2*n^3;forprime(p=3,n3/2,if(isprime(n3-p),k++));print1(k,", "))

Formula

a(n) = A002375(n^3).