A275023 Cubes c such that c + 2 and c - 2 are semiprime.

8, 216, 1331, 2197, 4913, 9261, 15625, 35937, 59319, 68921, 117649, 185193, 421875, 531441, 658503, 704969, 1030301, 1367631, 3723875, 5268024, 5359375, 11390625, 13651919, 16581375, 17779581, 19902511, 23149125, 25672375, 29503629, 36264691, 38958219, 40353607

Offset: 1

Author

K. D. Bajpai, Nov 12 2016

Keywords

• nonn

Comments

Intersection of A000578 and A105571.

Examples

			a(1) = 8 = 2^3. Also, 8 + 2 = 10 = 2*5; 8 - 2 = 6 = 2*3; both are semiprime.
a(2) = 216 = 6^3. Also, 216 + 2 = 218 = 2*109; 216 - 2 = 214 = 2*107; both are semiprime.
		

Links

• K. D. Bajpai, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000578, A001358, A105571, A278022.

Programs

Mathematica

Select[Table[n^3, {n, 1000}], PrimeOmega[# + 2] == 2 && PrimeOmega[# - 2] == 2 &]

PARI

for (n = 1, 1000, s = n^3; if(bigomega (s+2) == 2 && bigomega (s-2) == 2, print1 (s, ", ")))