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Search: id:A079215
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| A079215 |
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Catalan paths: numbers starting with 1 and ending with 1 where each digit is positive and adjacent digits differ by 1. |
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+0
2
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| 1, 121, 12121, 12321, 1212121, 1212321, 1232121, 1232321, 1234321, 121212121, 121212321, 121232121, 121232321, 121234321, 123212121, 123212321, 123232121, 123232321, 123234321, 123432121, 123432321, 123434321, 123454321
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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a(6917) cannot easily be written in decimal.
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FORMULA
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a(n) =A079214(n)+(10^(2+floor[log_10(A079214(n))])-1)/9.
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EXAMPLE
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Can be constructed from A063171 by starting from a leading 1 and adding 1 to previous digit of a(n) if next digit of A063171 is 1, and subtracting 1 if next digit is 0: e.g. A063171(3)=1100, so digits of a(3) are 1, 1+1=2, 2+1=3, 3-1=2 and 2-1=1 giving a(3)=12321.
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CROSSREFS
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Cf. A063171, A079214. a(n) has A000108(m) values with 2m+1 digits. Among the values with 2m+1 digits, the digit k appears a total of A039598(m, k-1) times.
Sequence in context: A036508 A054319 A006061 this_sequence A137466 A062689 A057139
Adjacent sequences: A079212 A079213 A079214 this_sequence A079216 A079217 A079218
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KEYWORD
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base,nonn
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AUTHOR
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Henry Bottomley (se16(AT)btinternet.com), Jan 02 2003
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