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Search: id:A109025
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| A109025 |
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5-almost primes (A014613) whose digit reversal is different and also has 5 prime factors (with multiplicity). "Emirp Tsolma-5.". |
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9
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| 270, 1386, 1575, 2070, 2136, 2142, 2295, 2300, 2394, 2412, 2475, 2508, 2550, 2565, 2568, 2610, 2844, 2964, 3087, 3267, 3465, 3654, 3708, 3924, 4008, 4016, 4068, 4185, 4208, 4290, 4293, 4347, 4446, 4482, 4563, 4692, 4779, 4875, 4932, 5049, 5238, 5355
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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This sequence is the k = 5 instance of the series which begins with k = 1 (emirps), k = 2 (emirpimes), k = 3 (emirp tsolma-3 = A109023), k = 4 (emirp tsolma-4 = A109024).
The Mma code for this was written by Ray Chandler who extended this sequence. He also has more values.
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REFERENCES
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Jonathan Vos Post, "1066 and All That: Emirp Tsolma-3 and Related Integer Sequences." Forthcoming paper on this sequence.
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LINKS
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Eric Weisstein's World of Mathematics, Almost Prime.
Eric Weisstein's World of Mathematics, Emirp.
Eric Weisstein and Jonathan Vos Post, Emirpimes.
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EXAMPLE
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a(2) = 1386 is in this sequence because 1386 = 2 * 3^2 * 7 * 11 is a 5-almost prime, and reverse(1386) = 6831 = 3^3 * 11 * 23 is also a 5-almost prime.
5355 is in this sequence because 5355 = 3^2 * 5 * 7 * 17, and reverse(5355) = 5535 = 3^3 * 5 * 41, although it is mere coincidence that 5355 is concatenated from entirely prime digits.
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CROSSREFS
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Cf. A006567, A097393, A109018, A109024, A109026-A109131.
Sequence in context: A025394 A029770 A028529 this_sequence A028535 A108094 A104844
Adjacent sequences: A109022 A109023 A109024 this_sequence A109026 A109027 A109028
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KEYWORD
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nonn,base
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AUTHOR
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Jonathan Vos Post (jvospost2(AT)yahoo.com), Jun 16 2005
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