A122732 - OEIS

%I #11 Feb 05 2017 02:54:39

%S 28,370,539,637,730,854,1001,1358,1547,1729,2198,2261,3059,3887,3925,

%T 4075,4123,4706,4825,4921,5038,5957,6293,6886,6923,7075,7163,7202,

%U 7657,8029,8729,9262,9269,9325,9331,10745,10955,11458,12175,12383,12845

%N 3-almost primes that are the sum of 2 positive cubes. Sums of 2 positive cubes, with the sums having exactly 3 prime divisors counted with multiplicity.

%C 3-almost prime analog of A085366 Semiprimes that are the sum of two positive cubes. The sum of two positive cubes cannot be prime.

%H Giovanni Resta, <a href="/A122732/b122732.txt">Table of n, a(n) for n = 1..10000</a>

%F A003325 INTERSECTION A014612. {x = a^3 + b^3 for positive integers a, b, such that A001222(x) = 3}.

%e a(1) = 28 = 2^2 * 7 = 1^3 + 3^3.

%e a(2) = 370 = 2 * 5 * 37 = 3^3 + 7^3.

%e a(3) = 539 = 7^2 * 11 = 2^3 + 8^3.

%e a(4) = 637 = 7^2 * 13 = 5^3 + 8^3.

%e a(5) = 730 = 2 * 5 * 73 = 1^3 + 9^3.

%e a(6) = 854 = 2 * 7 * 61 = 5^3 + 9^3.

%e a(7) = 1001 = 7 * 11 * 13 = 1^3 + 10^3.

%o (PARI) is(n)=bigomega(n)==3 && #select(v->min(v[1], v[2])>0, thue('x^3+1, n))>0 \\ _Charles R Greathouse IV_, Feb 05 2017

%Y Cf. A000578, A001222, A003325, A014612.

%K easy,nonn

%O 1,1

%A _Jonathan Vos Post_, Sep 23 2006

%E More terms from _R. J. Mathar_, Jan 27 2009