A130593 Evil semiprimes.

6, 9, 10, 15, 33, 34, 39, 46, 51, 57, 58, 65, 77, 85, 86, 95, 106, 111, 119, 123, 129, 141, 142, 159, 166, 169, 177, 178, 183, 187, 201, 202, 209, 215, 219, 221, 226, 235, 237, 249, 267

Offset: 1

Author

Jonathan Vos Post, Jun 16 2007

Keywords

• easy
• base
• nonn

Comments

Products of two (not necessarily distinct) primes such that the product has an even number of 1's in its binary expansion. Non-evil semiprimes are odious (A000069).

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000
• E. Fouvry, C. Mauduit, Sommes des chiffres et nombres presque premiers, (French) [Sums of digits and almost primes] Math. Ann. 305 (1996), no. 3, 571--599. MR1397437 (97k:11029).

Crossrefs

Cf. A000069, A001358, A001969.

Programs

Mathematica

Select[Range[300],PrimeOmega[#]==2&&EvenQ[DigitCount[#,2,1]]&] (* Harvey P. Dale, Nov 08 2011 *)

PARI

list(lim)=my(v=List(), t); forprime(p=2, lim\2, forprime(q=2, min(p,lim\p), if(hammingweight(n=p*q)%2,,listput(v, n)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Mar 26 2013

Formula

A001358 INTERSECTION A001969.

Extensions

Corrected (a(21)=129 added) by Harvey P. Dale, Nov 08 2011