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Search: id:A109023
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| A109023 |
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3-almost primes (A014612) whose digit reversal is different and also has 3 prime factors (with multiplicity). "Emirp Tsolma-3.". |
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+0
11
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| 117, 147, 165, 244, 246, 285, 286, 290, 338, 366, 369, 406, 418, 425, 435, 438, 442, 475, 498, 506, 507, 508, 524, 534, 539, 548, 561, 574, 582, 604, 605, 609, 628, 642, 663, 670, 682, 705, 711, 741, 759, 805, 814, 826, 833, 834, 845, 890, 894, 906, 1002
(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 = 3 instance of the series which begins with k = 1 (emirps), k = 2 (emirpimes). Forthcoming paper on this sequence: "Jonathan Vos Post, "1066 and All That: Emirp Tsolma-3 and Related Integer Sequences."
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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Ball, W. W. R. and Coxeter, H. S. M. Mathematical Recreations and Essays, 13th ed. New York: Dover, pp. 14-15, 1987.
Edalj, J. Problem 1622. Interm. de Math. 16, 34, 1909.
Jonesco, J. Problem 1622. Interm. de Math. 15, 128, 1908.
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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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1066 is in this sequence because 1066 = 2 * 13 * 41, making it a 3-almost prime, and reverse(1066) = 6601 = 7 * 23 * 41, also a 3-almost prime.
2001 is in this sequence because 2001 = 3 * 23 * 29, and reverse(2001) = 1002 = 2 * 3 * 167.
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CROSSREFS
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Cf. A006567, A097393, A109018, A109024-A109131.
Sequence in context: A084344 A015706 A095625 this_sequence A112877 A064180 A050245
Adjacent sequences: A109020 A109021 A109022 this_sequence A109024 A109025 A109026
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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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