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

1,1

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

Table of n, a(n) for n=1..40.

Index to sequences related to sums of cubes.

Formula

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

Mathematica

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

Prog

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

Crossrefs

Cf. A120398, A138854.

Sequence in context: A044408 A044789 A245005 * A324632 A251078 A153676

Adjacent sequences: A138852 A138853 A138854 * A138856 A138857 A138858

Keyword

nonn

Author

M. F. Hasler, Apr 13 2008

Status

approved