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Search: id:A154951
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| A154951 |
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Found by taking the tree defined by the Hofstadter H-sequence (A005374), mirroring it left to right and relabeling the nodes so they increase left to right. a(n) is the parent node of node n in the tree so constructed. |
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+0
1
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| 0, 1, 1, 2, 3, 4, 4, 5, 6, 6, 7, 8, 9, 9, 10, 10, 11, 12, 13, 13, 14, 15, 15, 16, 16, 17, 18, 19, 19, 20, 21, 22, 22, 23, 24, 24, 25, 25, 26, 27, 28, 28, 29, 29, 30, 31, 32, 32, 33, 34, 35, 35, 36, 37, 37, 38, 38, 39, 40, 41, 41, 42, 43, 43, 44, 44, 45, 46, 47, 47
(list; graph; listen)
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OFFSET
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0,4
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REFERENCES
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D. R. Hofstadter, Goedel, Escher, Bach: an Eternal Golden Braid, Basic Books, 1999, p. 137.
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LINKS
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David Fifield Table of n, a(n) for n=0..10000
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PROGRAM
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(Python) # Emulate a breadth-first traversal of the "flip"
# of the tree defined by the Hofstadter H-sequence.
.def hflip_iter():
....yield 0
....yield 1
....# Start on the first node of a left branch, parent node is 1.
....queue = [(1, 1)]
....n = 2
....while True:
........parent, state = queue.pop(0)
........yield parent
........if state == 0:
............# Root node. Add the two children.
............queue.append((n, 1))
............queue.append((n, 0))
........elif state == 1:
............# First node on left branch. Add the second node.
............queue.append((n, 2))
........elif state == 2:
............# Second node on left branch. Add a new root.
............queue.append((n, 0))
........n += 1
.i = hflip_iter()
.for n in range(0, 10001):
....print "%d %d" % (n, i.next())
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CROSSREFS
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Cf. A005374, A123070.
Sequence in context: A039708 A094500 A049473 this_sequence A095769 A080820 A116549
Adjacent sequences: A154948 A154949 A154950 this_sequence A154952 A154953 A154954
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KEYWORD
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nonn
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AUTHOR
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David Fifield (david(AT)bamsoftware.com), Jan 17 2009
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