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Search: id:A061715
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| A061715 |
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Numbers which are sandwiched between two numbers having the same ordered canonical form. |
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+0
4
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| 4, 6, 12, 18, 30, 34, 42, 56, 60, 72, 86, 92, 94, 102, 108, 138, 142, 144, 150, 160, 180, 184, 186, 192, 198, 202, 204, 214, 216, 218, 220, 228, 236, 240, 248, 266, 270, 282, 300, 302, 304, 312, 320, 322, 328, 340, 348, 392, 394, 412, 414, 416, 420, 424, 432
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The average of twin primes is a member. Is there ever a prime in the sequence?
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EXAMPLE
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34 is sandwiched between 33 and 35 which are of the form p*q where p and q are primes.
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MATHEMATICA
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f[n_] := Flatten[Table[{ # [[2]]}] & /@ FactorInteger[n]]; Drop[ Select[ Range[415], Sort[f[ # - 1]] == Sort[f[ # + 1]] & ], 1]
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CROSSREFS
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Cf. A074497, A074498.
Sequence in context: A130441 A068570 A074998 this_sequence A072570 A014574 A034425
Adjacent sequences: A061712 A061713 A061714 this_sequence A061716 A061717 A061718
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KEYWORD
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easy,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 21 2002
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EXTENSIONS
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Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 22 2002
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