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

1,1

Comments

Intersection of A000578 and A105571.

Links

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

Example

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.

Mathematica

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

Prog

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

Crossrefs

Cf. A000578, A001358, A105571, A278022.

Sequence in context: A072159 A016827 A239222 * A163289 A060459 A007409

Adjacent sequences: A275020 A275021 A275022 * A275024 A275025 A275026

Keyword

nonn

Author

K. D. Bajpai, Nov 12 2016

Status

approved