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A044028
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Numbers k such that 4 and 7 occur juxtaposed in the base-10 representation of k but not of k+1.
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0
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47, 74, 147, 174, 247, 274, 347, 374, 447, 479, 547, 574, 647, 674, 749, 774, 847, 874, 947, 974, 1047, 1074, 1147, 1174, 1247, 1274, 1347, 1374, 1447, 1479, 1547, 1574, 1647, 1674, 1749, 1774, 1847, 1874, 1947, 1974, 2047
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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okQ[n_]:=Module[{sidn=Sort/@Partition[IntegerDigits[n], 2, 1]}, MemberQ[sidn, {4, 7}]]; Select[Range[2100], okQ[#]&&!okQ[#+1]&] (* Harvey P. Dale, Feb 14 2012 *)
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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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