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A297128
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Numbers having an up-first zigzag pattern in base 4; see Comments.
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4
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6, 7, 11, 24, 25, 27, 28, 29, 30, 44, 45, 46, 97, 98, 99, 100, 102, 103, 108, 109, 110, 113, 114, 115, 116, 118, 119, 120, 121, 123, 177, 178, 179, 180, 182, 183, 184, 185, 187, 388, 390, 391, 392, 393, 395, 396, 397, 398, 401, 402, 403, 408, 409, 411, 412
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OFFSET
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1,1
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COMMENTS
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A number n having base-b digits d(m), d(m-1), ..., d(0) such that d(i) != d(i+1) for 0 <= i < m shows a zigzag pattern of one or more segments, in the following sense. Writing U for up and D for down, there are two kinds of patterns: U, UD, UDU, UDUD, ... and D, DU, DUD, DUDU, ... . In the former case, we say n has an "up-first zigzag pattern in base b"; in the latter, a "down-first zigzag pattern in base b". Example: 2,4,5,3,0,1,4,2 has segments 2,4,5; 5,3,0; 0,1,4; and 4,2, so that 24530142, with pattern UDUD, has an up-first zigzag pattern in base 10, whereas 4,2,5,3,0,1,4,2 has a down-first pattern. The sequences A297128..A297130 partition the natural numbers. See the guide at A297146.
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LINKS
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Table of n, a(n) for n=1..55.
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EXAMPLE
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Base-4 digits of 3003: 2,3,2,3,2,3, with pattern UDUDU, so that 3003 is in the sequence.
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MATHEMATICA
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a[n_, b_] := Sign[Differences[IntegerDigits[n, b]]]; z = 300;
b = 4; t = Table[a[n, b], {n, 1, 10*z}];
u = Select[Range[z], ! MemberQ[t[[#]], 0] && First[t[[#]]] == 1 &] (* A297128 *)
v = Select[Range[z], ! MemberQ[t[[#]], 0] && First[t[[#]]] == -1 &] (* A297129 *)
Complement[Range[z], Union[u, v]] (* A297130 *)
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CROSSREFS
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Cf. A297129, A297130.
Sequence in context: A347512 A296695 A228948 * A035110 A011990 A105085
Adjacent sequences: A297125 A297126 A297127 * A297129 A297130 A297131
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KEYWORD
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nonn,easy,base
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AUTHOR
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Clark Kimberling, Jan 13 2018
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STATUS
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approved
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