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A324928
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Matula-Goebel numbers of rooted trees of depth 3.
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5
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5, 10, 13, 15, 17, 20, 23, 25, 26, 30, 34, 35, 37, 39, 40, 43, 45, 46, 50, 51, 52, 60, 61, 65, 67, 68, 69, 70, 73, 74, 75, 78, 80, 85, 86, 89, 90, 91, 92, 95, 100, 102, 103, 104, 105, 107, 111, 115, 117, 119, 120, 122, 125, 129, 130, 134, 135, 136, 138, 140
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OFFSET
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1,1
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COMMENTS
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Numbers n such that A109082(n) = 3.
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LINKS
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EXAMPLE
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The sequence of all rooted trees of depth 3 together with their Matula-Goebel numbers begins:
5: (((o)))
10: (o((o)))
13: ((o(o)))
15: ((o)((o)))
17: (((oo)))
20: (oo((o)))
23: (((o)(o)))
25: (((o))((o)))
26: (o(o(o)))
30: (o(o)((o)))
34: (o((oo)))
35: (((o))(oo))
37: ((oo(o)))
39: ((o)(o(o)))
40: (ooo((o)))
43: ((o(oo)))
45: ((o)(o)((o)))
46: (o((o)(o)))
50: (o((o))((o)))
51: ((o)((oo)))
52: (oo(o(o)))
60: (oo(o)((o)))
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MATHEMATICA
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Select[Range[100], Length[NestWhileList[Times@@PrimePi/@FactorInteger[#][[All, 1]]&, #, #>1&]]-1==3&]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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