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A092739
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Numbers n such that n*(n+1)/2 is the juxtaposition of two identical strings in binary representation.
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1
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2, 4, 5, 8, 9, 16, 17, 32, 33, 44, 64, 65, 90, 128, 129, 171, 256, 257, 512, 513, 702, 1024, 1025, 2048, 2049, 2732, 4096, 4097, 5542, 8192, 8193, 10923, 16384, 16385, 17515, 22939, 32768, 32769, 40050, 43361, 65536, 65537, 131072, 131073, 174764
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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17*(17+1)/2= 153 = 9*2^4 + 9 -> '10011001' -> '1001''1001', therefore 17 is a term.
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MATHEMATICA
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tisbQ[n_]:=Module[{idn=IntegerDigits[(n(n+1))/2, 2], len}, len=Length[idn]; EvenQ[ len]&&Take[idn, len/2]==Take[idn, -len/2]]; Select[Range[ 180000], tisbQ] (* Harvey P. Dale, Aug 08 2016 *)
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PROG
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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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