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Search: id:A046328
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| A046328 |
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Palindromes with exactly 2 prime factors (counted with multiplicity). |
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+0
8
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| 4, 6, 9, 22, 33, 55, 77, 111, 121, 141, 161, 202, 262, 303, 323, 393, 454, 505, 515, 535, 545, 565, 626, 707, 717, 737, 767, 818, 838, 878, 898, 939, 949, 959, 979, 989, 1111, 1441, 1661, 1991, 3113, 3223, 3443, 3883, 7117, 7447, 7997, 9119, 9229, 9449, 10001
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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E.g. 111 is a palindrome and 111 = 3*37. 3 and 37 are primes.
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MATHEMATICA
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fQ[n_] := Block[{id = IntegerDigits[n]}, Plus @@ Last /@ FactorInteger[n] == 2 && id == Reverse[id]]; Select[ Range[ 10000], fQ[ # ] &] (from Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 06 2005)
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CROSSREFS
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Cf. A001358, A046315, A046408, A108505.
Sequence in context: A046338 A118690 A084994 this_sequence A046376 A085721 A081614
Adjacent sequences: A046325 A046326 A046327 this_sequence A046329 A046330 A046331
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KEYWORD
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nonn,base
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AUTHOR
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Patrick De Geest (pdg(AT)worldofnumbers.com), Jun 15 1998.
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