A138855 Half-sum (or average) of cubes of two distinct odd primes.

76, 185, 234, 679, 728, 837, 1112, 1161, 1270, 1764, 2470, 2519, 2628, 3122, 3443, 3492, 3555, 3601, 4095, 4528, 5886, 6097, 6146, 6255, 6749, 7182, 8540, 9513, 12208, 12257, 12366, 12860, 13293, 14651, 14909, 14958, 15067, 15561, 15624, 15994

Offset: 1

Author

M. F. Hasler, Apr 13 2008

Keywords

• nonn

Comments

Even terms of A120398, divided by two. (Terms in A120398 are even iff they are the sum of two odd prime cubes.) Also, even terms of A138854 divided by two minus 4

Links

• Index to sequences related to sums of cubes.

Crossrefs

Cf. A120398, A138854.

Programs

Mathematica

With[{nn=40},Take[Union[Mean/@(Subsets[Prime[Range[2,nn/2]],{2}]^3)],nn]] (* Harvey P. Dale, Nov 16 2013 *)

PARI

for(n=1,10^5, isA120398(2*n) & print1(n", "))

Formula

A138855 = { ( prime(i)^3+prime(j)^3 )/2 ; i>j>1 } = (1/2) { even terms in A120398 } = { even terms in A138854 } / 2 - 4.