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

1,1

Comments

Semiprimes in A032793.

Links

K. D. Bajpai, Table of n, a(n) for n = 1..11280

Example

21 = 3 * 7 which is semiprime and 21 = 1 mod 5.
39 = 3 * 13 which is semiprime and 39 = 4 mod 5.

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 *)

Prog

(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

Crossrefs

Cf. A001358, A032793, A045371.

Sequence in context: A286303 A084336 A094750 * A330071 A057988 A175587

Adjacent sequences: A241010 A241011 A241012 * A241014 A241015 A241016

Keyword

nonn,easy

Author

K. D. Bajpai, Aug 07 2014

Status

approved