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 A126601 a(n) = n-th composite from among those composites which are coprime to n. 1
 4, 15, 10, 25, 12, 77, 15, 39, 26, 69, 20, 121, 22, 81, 56, 69, 27, 161, 30, 121, 65, 105, 35, 205, 49, 119, 68, 141, 44, 391, 46, 123, 92, 141, 81, 287, 54, 153, 106, 213, 58, 425, 62, 185, 146, 177, 66, 343, 82, 259, 128, 209, 75, 385, 114, 253, 142, 215, 82, 671, 85 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Michel Marcus, Table of n, a(n) for n = 1..1000 EXAMPLE The composites which are coprime to 6 are: 25,35,49,55,65,77,85,...So a(6) is the 6th of these, which is 77. MATHEMATICA f[n_] := Block[{k = 1, c = n}, While[c > 0, k++; While[PrimeQ[k] || GCD[k, n] > 1, k++ ]; c--; ]; k]; Table[f[n], {n, 61}] (* Ray Chandler, Jan 08 2007 *) PROG (PARI) a(n) = {my(c=2, nb=0); while(nb != n, c++; if (!isprime(c) && (gcd(c, n)==1), nb++)); c; } \\ Michel Marcus, Sep 06 2019 CROSSREFS Cf. A089090 (the 1st such composite). Sequence in context: A143899 A154068 A309526 * A284119 A290377 A332767 Adjacent sequences: A126598 A126599 A126600 * A126602 A126603 A126604 KEYWORD nonn AUTHOR Leroy Quet, Jan 06 2007 EXTENSIONS Extended by Ray Chandler, Jan 08 2007 STATUS approved

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Last modified October 2 14:06 EDT 2023. Contains 365837 sequences. (Running on oeis4.)