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A217790
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Composite evil numbers (A001969) having no proper evil divisors.
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2
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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
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OFFSET
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1,1
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COMMENTS
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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
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LINKS
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MATHEMATICA
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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 *)
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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