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A138720
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Concatenation of k digits 1, k digits 0 and k digits 1, where k is the n-th positive triangular number.
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4
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101, 111000111, 111111000000111111, 111111111100000000001111111111, 111111111111111000000000000000111111111111111, 111111111111111111111000000000000000000000111111111111111111111
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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MATHEMATICA
| Table[FromDigits[Join[PadRight[{}, (n(n+1))/2, 1], PadRight[{}, (n(n+1))/2, 0], PadRight[{}, (n(n+1))/2, 1]]], {n, 6}] (* From Harvey P. Dale, Dec 11 2011 *)
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CROSSREFS
| Cf. A000217, 138711, A138179, A138721, A138722.
Sequence in context: A138120 A082521 A138826 * A006064 A015164 A204749
Adjacent sequences: A138717 A138718 A138719 * A138721 A138722 A138723
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KEYWORD
| base,easy,nonn
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AUTHOR
| Omar E. Pol (info(AT)polprimos.com), Mar 29 2008
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