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Search: id:A121599
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| A121599 |
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a(1)=1. a(n) = number of earlier terms which are not divisible by the smallest prime dividing n. |
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+0
2
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| 1, 1, 2, 2, 4, 2, 6, 2, 7, 3, 10, 4, 12, 4, 11, 5, 16, 6, 18, 6, 14, 6, 22, 6, 22, 6, 17, 7, 28, 8, 30, 8, 22, 8, 31, 9, 36, 10, 26, 10, 40, 10, 42, 10, 31, 11, 46, 12, 43, 13, 36, 14, 52, 14, 46, 14, 41, 15, 58, 16, 60, 16, 45, 17, 53, 19, 66, 20, 49, 21, 70, 22, 72, 22, 53, 23, 65
(list; graph; listen)
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OFFSET
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1,3
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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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2 is the smallest prime dividing 12. Among the first 11 terms of the sequence there are 4 terms (1,1,7,3) which are not divisible by 2. So a(12) = 4.
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MATHEMATICA
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f[s_] := Append[s, Length@ Select[s, Mod[ #, FactorInteger[1 + Length@s][[1, 1]]] != 0 &]]; Nest[f, {1}, 76] (* Robert G. Wilson v *)
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PROGRAM
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(PARI) {m=78; print1(a=1, ", "); v=[a]; for(n=2, m, p=factor(n)[1, 1]; a=0; for(j=1, n-1, if(v[j]%p>0, a++)); print1(a, ", "); v=concat(v, a))} - (Klaus Brockhaus, Aug 15 2006)
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CROSSREFS
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Cf. A096216, A121600.
Sequence in context: A117004 A128982 A096216 this_sequence A080221 A137849 A118982
Adjacent sequences: A121596 A121597 A121598 this_sequence A121600 A121601 A121602
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Aug 09 2006
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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, Aug 15 2006
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