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Search: id:A114802
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| A114802 |
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3-concatenation-free sequence starting (1,2). |
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+0
1
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| 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 20, 100, 121, 122, 130, 131, 140, 141, 150, 151, 160, 161, 170, 171, 180, 181, 190, 191, 200, 212, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 240, 250, 260, 270, 280, 290, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Starting with the terms (1,2) this sequence consists of minimum increasing integer terms such that no term is the concatenation of any three previous terms. The next consecutive number skipped after 121 is 123 = Concatenate(1,2,3); the sequence then resumes with 130, 131, skips 132 = Concatenate(1,3,2), and so on. This is the analogue of a 3-Stoehr sequence with concatenation (base 10) substituting for addition. A026474 is a 3-Stoehr sequence. Stoehr is actually spelled St[o with umlaut]hr.
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LINKS
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Eric Weisstein's World of Mathematics, Stoehr Sequence.
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FORMULA
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a(0) = 1, a(1) = 2, for n>2: a(n) = least k > a(n-1) such that k is not an element of {Concatenate[a(h),a(i),a(j)]} for any three distinct a(h)<a(n-1), a(i)<a(n-1), and a(j)<a(n-1).
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CROSSREFS
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Cf. A084383, A033627, A026474.
Sequence in context: A132578 A101318 A114801 this_sequence A130575 A068637 A064222
Adjacent sequences: A114799 A114800 A114801 this_sequence A114803 A114804 A114805
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KEYWORD
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base,easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Feb 18 2006
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