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A141551
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Numbers n with property that if d divides n, then tau(tau(d)) also divides n.
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2
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1, 2, 4, 6, 12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132, 144, 156, 180, 192, 204, 228, 240, 252, 276, 288, 300, 324, 348, 360, 372, 396, 444, 468, 480, 492, 516, 564, 576, 588, 600, 612, 636, 684, 708, 720, 732, 804, 828, 840, 852, 876, 900, 948, 960, 972, 996, 1044, 1068
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| tau() = A000005().
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MAPLE
| with(numtheory); isA141551 := proc(n) local dvs, d; dvs := divisors(n) ; for d in dvs do if not tau(tau(d)) in dvs then RETURN(false): fi; od: RETURN(true); end:
t1:=[]; for n from 1 to 60000 do if isA141551(n) then t1:=[op(t1), n]; fi; od:
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CROSSREFS
| Cf. A141586.
Sequence in context: A168264 A056795 A141420 * A181804 A094348 A189686
Adjacent sequences: A141548 A141549 A141550 * A141552 A141553 A141554
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Sep 12 2008
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