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A125494
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Composite evil numbers.
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1
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6, 9, 10, 12, 15, 18, 20, 24, 27, 30, 33, 34, 36, 39, 40, 45, 46, 48, 51, 54, 57, 58, 60, 63, 65, 66, 68, 72, 75, 77, 78, 80, 85, 86, 90, 92, 95, 96, 99, 102, 105, 106, 108, 111, 114, 116, 119, 120, 123, 125, 126, 129, 130, 132, 135, 136, 141, 142, 144, 147, 150, 153
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OFFSET
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1,1
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LINKS
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EXAMPLE
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12 is in the sequence since it is composite and its base-2 representation (1100) has an even number of 1's.
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MAPLE
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a:=proc(n) local n2: n2:=convert(n, base, 2): if add(n2[j], j=1..nops(n2)) mod 2 = 0 and isprime(n)=false then n else fi end: seq(a(n), n=1..180); # Emeric Deutsch, Jan 01 2007
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MATHEMATICA
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Select[Range[153], EvenQ @ DigitCount[#, 2][[1]] && CompositeQ[#] &] (* Amiram Eldar, Dec 09 2019 *)
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PROG
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(PARI) isok(n) = (n>0) && !isprime(n) && !(hammingweight(n) % 2); \\ Michel Marcus, Mar 29 2019
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CROSSREFS
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Intersection of A002808 (composite numbers) and A001969 (evil numbers).
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KEYWORD
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base,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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