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A093685
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In binary representation: numbers not occurring in their factorial.
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5
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0, 5, 11, 13, 15, 17, 31, 37, 55, 81, 164, 395, 513, 517, 619, 1041, 1287, 1538, 2108, 2116, 2137, 2138, 2282, 2352, 2363, 2432, 2466, 2524, 4278, 4511, 4758, 4766, 4852, 4854, 5136, 5586, 8396, 8463, 8883, 9707, 10351, 16528, 17279, 19469, 21244, 24472
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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5! = 1*2*3*4*5 = 120 -> '1111000', in which '101'=5 is not contained, so 5 is in the sequence.
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MATHEMATICA
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f[n_] := ToString[ FromDigits[ IntegerDigits[n, 2]]]; Select[ Range[ 29000], StringPosition[ f[ #! ], f[ # ]] == {} &] (* Robert G. Wilson v, Apr 15 2004 *)
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PROG
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(Python)
def aupto(limit):
kfact, alst = 1, [0]
for k in range(1, limit+1):
kb, kfact = bin(k)[2:], kfact * k
kfactb = bin(kfact)[2:]
if kb not in kfactb: alst.append(k)
return alst
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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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EXTENSIONS
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STATUS
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approved
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