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Search: id:A074998
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| A074998 |
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Composite numbers which are sandwiched between two numbers having the same unordered canonical form. |
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+0
2
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| 4, 6, 12, 18, 30, 34, 42, 51, 55, 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, 243, 248, 249, 266, 270, 282, 300, 302, 304, 312, 320, 322, 328, 340, 341, 348, 392, 394, 412
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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The average of twin primes is a member.
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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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MAPLE
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k := 0: for j from 2 to 5000 do if not isprime(j) then a := ifactors(j-1): b := ifactors(j+1): if sort([seq(a[2][i][2], i= 1..nops(a[2]))])= sort([seq(b[2][i][2], i= 1..nops(b[2]))]) then k := k+1: c[k] := j: fi: fi: od: seq(c[i], i= 1..k);
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CROSSREFS
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Cf. A074997, A061715, A074460.
Sequence in context: A109290 A130441 A068570 this_sequence A061715 A072570 A014574
Adjacent sequences: A074995 A074996 A074997 this_sequence A074999 A075000 A075001
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KEYWORD
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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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More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Aug 22 2002
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