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A059941
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Take the n-th number which is just a sequence of 1's and 2's (A007931): if the first k digits in order are the same as the last k digits in order then put 1 in the k-th from right digit of a(n), otherwise put a zero.
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3
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1, 1, 11, 10, 10, 11, 111, 100, 101, 100, 100, 101, 100, 111, 1111, 1000, 1001, 1000, 1001, 1010, 1001, 1000, 1000, 1001, 1010, 1001, 1000, 1001, 1000, 1111, 11111, 10000, 10001, 10000, 10011, 10000, 10001, 10000, 10001, 10010, 10101, 10000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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EXAMPLE
| a(35)=10011 since the 35th number with 1's and 2's is 11211, the fist digit and last digit are the same (1), the first two and the last two are the same (11), the first three and last three are not (112 and 211), the first four and last four are not (1121 and 1211) and the first five and last five are (11211).
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MATHEMATICA
| a[n_] := (id = Drop[ IntegerDigits[n+1, 2], 1] + 1; an = {}; Do[ PrependTo[an, If[Take[id, k] == Take[id, -k], 1, 0]], {k, 1, Length[id]}]; FromDigits[an]); Table[a[n], {n, 1, 42}](* From Jean-François Alcover, Nov 21 2011 *)
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CROSSREFS
| A059942 is this sequence translated from binary to decimal. Cf. A007931, A059943.
Sequence in context: A004452 A112952 A070561 * A086100 A182782 A004283
Adjacent sequences: A059938 A059939 A059940 * A059942 A059943 A059944
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KEYWORD
| base,nonn
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AUTHOR
| Henry Bottomley (se16(AT)btinternet.com), Feb 14 2001
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