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Search: id:A114453
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| A114453 |
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Number of 5-almost primes less than or equal to 10^n. |
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+0
14
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| 0, 0, 4, 76, 963, 11185, 124465, 1349779, 14371023, 150982388, 1570678136, 16218372618, 166497674684, 1701439985694, 17323079621014
(list; graph; listen)
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OFFSET
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0,3
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EXAMPLE
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There are 4 five-almost primes up to 100: 32,48,72&80.
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MATHEMATICA
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FiveAlmostPrimePi[n_] := Sum[ PrimePi[n/(Prime@i*Prime@j*Prime@k*Prime@l)] - l + 1, {i, PrimePi[n^(1/5)]}, {j, i, PrimePi[(n/Prime@i)^(1/4)]}, {k, j, PrimePi[(n/(Prime@i*Prime@j))^(1/3)]}, {l, k, PrimePi[(n/(Prime@i*Prime@j*Prime@k))^(1/2)]}]; Table[ FiveAlmostPrimePi[10^n], {n, 0, 12}]
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CROSSREFS
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Cf. A006880, A066265, A109251, A014613, A116382.
Adjacent sequences: A114450 A114451 A114452 this_sequence A114454 A114455 A114456
Sequence in context: A101718 A094160 A045996 this_sequence A093184 A009631 A012020
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 07 2006
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EXTENSIONS
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a(13) and a(14) from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 07 2007
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