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Search: id:A023745
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| A023745 |
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Digits in base 3 are in nondecreasing order. |
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+0
5
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| 0, 1, 2, 4, 5, 8, 13, 14, 17, 26, 40, 41, 44, 53, 80, 121, 122, 125, 134, 161, 242, 364, 365, 368, 377, 404, 485, 728, 1093, 1094, 1097, 1106, 1133, 1214, 1457, 2186, 3280, 3281, 3284, 3293, 3320, 3401, 3644, 4373, 6560, 9841, 9842, 9845, 9854
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OFFSET
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0,3
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FORMULA
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Numbers that in ternary are the concatenation of i 1's with j 2's, i, j>=0. Also a(n) = A073216(n+1) - 1. Proof: Write a(n) as 1{m}2{n}, then adding 1 gives 1{m-1}20{n} for m>0 and 10{n} for m=0. Doubling yields 10{m-1}10{n} or 20{n}, respectively. These two forms exactly describe the forms of sums of two powers of 3, the two powers being 3^n and 3^(m+n). - Hugo van der Sanden.
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CROSSREFS
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Sequence in context: A116901 A102829 A031988 this_sequence A085443 A164571 A105134
Adjacent sequences: A023742 A023743 A023744 this_sequence A023746 A023747 A023748
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KEYWORD
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nonn,base,easy
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AUTHOR
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Olivier Gerard (olivier.gerard(AT)gmail.com)
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