A217790 Composite evil numbers (A001969) having no proper evil divisors.

77, 169, 209, 287, 329, 343, 407, 413, 427, 469, 533, 553, 649, 679, 703, 763, 869, 893, 917, 931, 1121, 1133, 1169, 1253, 1271, 1331, 1337, 1351, 1369, 1391, 1393, 1457, 1477, 1501, 1517, 1589, 1631, 1661, 1757, 1781, 1813, 1829, 1963, 1991, 2033, 2191, 2209

Offset: 1

Author

Vladimir Shevelev, Mar 28 2013

Keywords

• nonn
• base

Comments

The sequence is obtained using Eratosthenes-like sieve for evil numbers.

a(10^2) = 4367, a(10^3) = 40247, a(10^4) = 407659, a(10^5) = 4434067. - Giovanni Resta, Mar 28 2013

Links

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

Crossrefs

Cf. A000069, A001969.

Programs

Mathematica

evilQ[n_] := EvenQ@Total@IntegerDigits[n, 2]; okQ[n_] := evilQ[n] && ! PrimeQ[n] && Catch[Do[If[evilQ[d], Throw[False]], {d, Most@Rest@Divisors@n}]; True]; Select[Range@3000, okQ] (* Giovanni Resta, Mar 28 2013 *)

PARI

isevil(n) = hammingweight(n) % 2 == 0;
noevildiv(n) = {fordiv(n, d, if ((d < n) && isevil(d), return (0));); 1;}
lista(nn) = {forcomposite(n=1, nn, if (isevil(n) && noevildiv(n), print1(n, ", ")););} \\ Michel Marcus, Feb 08 2016