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Search: id:A118310
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| A118310 |
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a(n) = GCD(n,m(n)), where m(n) is the n-th nonprime positive integer (1 or composite). |
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1
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| 1, 2, 3, 4, 1, 2, 1, 2, 3, 2, 1, 4, 1, 2, 3, 1, 1, 9, 1, 10, 1, 11, 1, 1, 1, 2, 3, 4, 1, 2, 1, 2, 3, 1, 5, 3, 1, 2, 1, 8, 1, 2, 1, 2, 9, 2, 1, 6, 1, 1, 1, 4, 1, 3, 1, 7, 3, 2, 1, 2, 1, 1, 1, 1, 1, 6, 1, 4, 3, 2, 1, 24, 1, 1, 25, 2, 1, 3, 1, 4, 1, 1, 1, 6, 5, 2, 3, 2, 1, 30, 1, 2, 3, 2, 5, 6, 1, 1, 1, 4, 1, 2, 1
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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For n >= 1, a(n+1) = GCD(n+1,c(n)), where c(n) = the n-th composite.
First occurrence of k: 1, 2, 3, 4, 35, 48, 56, 40, 18, 20, 22, 120, 130, 140, 375, ..., . - Robert G. Wilson v.
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MATHEMATICA
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NonPrime[n_Integer] := FixedPoint[n + PrimePi@# &, n + PrimePi@n]; f[n_] := GCD[n, NonPrime@n]; Array[f, 103] - Robert G. Wilson v
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PROGRAM
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(PARI) A002808(maxn)= { local(a); a=[4]; for(n=5, maxn, if( !isprime(n), a=concat(a, n); ); ); return(a); } A118310(maxn)= { local(nonppo, a, newa, nonppol); a=[; ]; nonppo=concat(1, A002808(maxn)); nonppol=matsize(nonppo); for(n=1, nonppol[2], newa= gcd(n, nonppo[n]); a=concat(a, newa); ); return(a); } print(A118310(180)); (Mathar)
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CROSSREFS
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Cf. A064814.
Sequence in context: A138297 A139458 A104412 this_sequence A073057 A084310 A078978
Adjacent sequences: A118307 A118308 A118309 this_sequence A118311 A118312 A118313
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), May 14 2006
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(at)rgwv.com) and R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 16 2006
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