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A109028
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Numbers that have exactly eight prime factors counted with multiplicity (A046310) whose digit reversal is different and also has 8 prime factors (with multiplicity).
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10
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16560, 25515, 27864, 42480, 46872, 51552, 57348, 61488, 65448, 67797, 69408, 69840, 79776, 80496, 84375, 84456, 88416, 105336, 119448, 125928, 160416, 167076, 202032, 204984, 206928, 210960, 211104, 211464, 213750, 213792, 213920, 213984
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OFFSET
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1,1
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COMMENTS
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This sequence is the k = 8 instance of the series which begins with k = 1 (emirps), k = 2, k = 3 (A109023), k = 4 (A109024), k = 5 (A109025), k = 6 (A109026), k = 7 (A109027).
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LINKS
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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) = 25515 is in this sequence because 25515 = 3^6 * 5 * 7 has exactly 8 prime factors counted with multiplicity and reverse(25515) = 51552 = 2^5 * 3^2 * 179 also has exactly 8 prime factors counted with multiplicity.
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PROG
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(PARI) is(n) = {
my(r = fromdigits(Vecrev(digits(n))));
n!=r && bigomega(n) == 8 && bigomega(r) == 8
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CROSSREFS
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Cf. A046310, A006567, A097393, A109018, A109023, A109024, A109025, A109026, A109027, A109029, A109030, A109031.
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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