A241013 Semiprimes congruent to {1, 2, 4} mod 5.
4, 6, 9, 14, 21, 22, 26, 34, 39, 46, 49, 51, 57, 62, 69, 74, 77, 82, 86, 87, 91, 94, 106, 111, 119, 121, 122, 129, 134, 141, 142, 146, 159, 161, 166, 169, 177, 187, 194, 201, 202, 206, 209, 214, 217, 219, 221, 226, 237, 247, 249, 254, 259, 262, 267, 274, 287, 289
Offset: 1
Examples
21 = 3 * 7 which is semiprime and 21 = 1 mod 5. 39 = 3 * 13 which is semiprime and 39 = 4 mod 5.
Links
- K. D. Bajpai, Table of n, a(n) for n = 1..11280
Programs
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Mathematica
Select[Range[500], PrimeOmega[#] == 2 && MemberQ[{1, 2, 4}, Mod[#, 5]] &](* Bajpai *) Select[Complement[Range[100], 5Range[20] - 2, 5Range[20]], PrimeOmega[#] == 2 &] (* Alonso del Arte, Aug 07 2014 *) -
PARI
for(n=1,10^4,if(n!=Mod(0,5)&&n!=Mod(3,5),if(bigomega(n)==2,print1(n,", ")))) \\ Derek Orr, Aug 07 2014
Comments