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Search: id:A114707
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| A114707 |
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a(1)=1. For n>1, a(n) = a(n-1) + (number of distinct primes dividing n but not a(n-1)). |
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+0
2
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| 1, 2, 3, 4, 5, 7, 7, 8, 9, 11, 11, 13, 13, 15, 15, 16, 17, 19, 19, 21, 21, 23, 23, 25, 25, 27, 27, 29, 29, 32, 33, 34, 36, 37, 39, 40, 41, 43, 45, 46, 47, 50, 51, 53, 55, 57, 58, 59, 60, 60, 61, 63, 64, 65, 66, 67, 69, 71, 72, 73, 74, 75, 76, 76, 78, 79, 80, 81, 82, 84, 85, 87
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Number of distinct primes dividing n but not A114707(n-1) is A114708(n).
a(10^k), k=0..6: 1, 11, 130, 1691, 19819, 220501, 2398245. - Robert G. Wilson v Dec 28 2005.
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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a(11) = 11. Since 2 and 3 are the 2 distinct primes that divide 12 and neither divides 11, a(12) is 2 greater than a(11), a(12) = 13.
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MATHEMATICA
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a[1] = 1; a[n_] := a[n] = a[n - 1] + Length@Complement[First /@ FactorInteger@n, First /@ FactorInteger@a[n - 1]]; Array[a, 72] (* Robert G. Wilson v *)
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PROGRAM
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(PARI) {print1(a=1, ", "); for(n=2, 72, print1(a=a+#setminus(Set(factor(n)[, 1]), Set(factor(a)[, 1])), ", "))} (Brockhaus)
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CROSSREFS
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Cf. A114708.
Sequence in context: A082025 A076034 A034152 this_sequence A000015 A122411 A117174
Adjacent sequences: A114704 A114705 A114706 this_sequence A114708 A114709 A114710
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Dec 26 2005
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EXTENSIONS
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More terms from Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Robert G. Wilson v (rgwv(at)rgwv.com), Dec 27 2005
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