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Search: id:A121600
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| A121600 |
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a(1)=1. a(n) = number of earlier terms which are not divisible by the largest prime dividing n. |
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+0
2
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| 1, 1, 2, 2, 4, 5, 6, 3, 6, 8, 10, 8, 12, 13, 12, 5, 16, 12, 18, 16, 20, 21, 22, 15, 19, 24, 16, 26, 28, 24, 30, 9, 31, 33, 32, 21, 36, 36, 36, 33, 40, 38, 42, 40, 36, 45, 46, 25, 44, 39, 50, 48, 52, 29, 50, 51, 54, 56, 58, 47, 60, 60, 57, 21, 60, 61, 66, 66, 67, 63, 70, 37, 72, 72
(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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3 is the largest prime dividing 12. Among the first 11 terms of the sequence there are 8 terms (1,1,2,2,4,5,8,10) which are not divisible by 3. So a(12) = 8.
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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=75; print1(a=1, ", "); v=[a]; for(n=2, m, f=factor(n); p=f[matsize(f)[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, A121599.
Sequence in context: A114701 A049269 A085085 this_sequence A126870 A137413 A010848
Adjacent sequences: A121597 A121598 A121599 this_sequence A121601 A121602 A121603
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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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