A180748 Numbers k such that k^2 - k + 1 is semiprime.

5, 8, 10, 11, 12, 14, 20, 24, 27, 29, 30, 32, 33, 35, 36, 37, 40, 41, 43, 44, 45, 46, 48, 49, 52, 53, 54, 57, 61, 64, 66, 71, 73, 74, 77, 83, 84, 85, 86, 87, 92, 93, 94, 96, 97, 98, 99, 104, 105, 109, 113, 114, 115, 116, 121, 123, 124, 125, 126, 127, 128, 130, 133, 135

Offset: 1

Author

Jason Earls, Sep 19 2010

Keywords

• easy
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001358, A002061.

Programs

Mathematica

Select[Range[135], PrimeOmega[#^2 - # + 1] == 2 &] (* Amiram Eldar, Dec 23 2019 *)