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Search: id:A131939
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| A131939 |
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Least k such that the difference between consecutive 3-almost primes A014612(k) equals n, or 0 if no such k exists. |
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+0
1
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| 5, 3, 13, 1, 10, 2, 4, 31, 32, 36, 12, 7, 136, 19, 302, 486, 1094, 73, 1366, 6763, 1092, 2006, 8924, 4785, 18345, 18487, 42798, 16571, 11095, 57831, 60912, 4528, 24846, 41304, 232350, 233678, 123279, 1779265, 740729, 177385, 1015228, 1772286
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OFFSET
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1,1
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COMMENT
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Index of smallest 3-almost prime gap equal to n. This is to 3-almost primes A014612 as A123375 is to semiprimes A001358. a(25) = 0 or a(25) > 10000. Conjecture: a(n) > 0 for all n.
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FORMULA
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a(n) = MIN{k such that A114403(k) = n, or 0 if no such k exists}. a(n) = MIN{k such that A014612(k+1) - A014612(k) = n, or 0 if no such k exists}.
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EXAMPLE
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a(1) = 5 because A014612(6)-A014612(5) = 28-27 = 1.
a(2) = 3 because A014612(4)-A014612(3) = 20-18 = 2.
a(3) = 13 because 66-63 = 3.
a(4) = 1 because 12-8 = 4.
a(5) = 10 because 50-45 = 5.
a(6) = 2 because 18-12 = 6.
a(7) = 4 because 27-20 = 7.
a(8) = 31 because 138-130 = 8.
a(9) = 32 because 147-138 = 9
a(10) = 36 because 164-154 = 10.
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CROSSREFS
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Cf. A014612, A114403, A123375.
Sequence in context: A141234 A130180 A104587 this_sequence A111744 A083781 A080797
Adjacent sequences: A131936 A131937 A131938 this_sequence A131940 A131941 A131942
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KEYWORD
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nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Oct 05 2007
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 07 2007
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