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 A205794 Least positive integer j such that n divides C(k)-C(j) , where k, as in A205793, is the least number for which there is such a j, and C=A002808 (composite numbers). 0

%I

%S 1,1,2,1,1,1,3,1,2,1,1,1,3,1,2,1,1,1,2,1,1,1,1,1,3,1,2,1,1,1,1,1,2,1,

%T 1,1,3,1,2,1,1,1,2,1,1,1,1,1,2,1,1,1,1,1,3,1,2,1,1,1,1,1,2,1,1,1,3,1,

%U 2,1,1,1,1,1,2,1,1,1,2,1,1,1,1,1,2,1,1,1,1,1,1,1,2,1,1,1,3,1,2

%N Least positive integer j such that n divides C(k)-C(j) , where k, as in A205793, is the least number for which there is such a j, and C=A002808 (composite numbers).

%C Is this sequence bounded? For a guide to related sequences, see A204892.

%e 1 divides C(2)-C(1) -> k=2, j=1

%e 2 divides C(2)-C(1) -> k=2, j=1

%e 3 divides C(4)-C(2) -> k=4, j=2

%e 4 divides C(3)-C(1) -> k=3, j=1

%e 5 divides C(4)-C(1) -> k=4, j=1

%e 6 divides C(5)-C(1) -> k=5, j=1

%t s = Select[Range[2, 120], ! PrimeQ[#] &]

%t lk = Table[

%t NestWhile[# + 1 &, 1,

%t Min[Table[Mod[s[[#]] - s[[j]], z], {j, 1, # - 1}]] =!= 0 &], {z, 1,

%t Length[s]}]

%t Table[NestWhile[# + 1 &, 1,

%t Mod[s[[lk[[j]]]] - s[[#]], j] =!= 0 &], {j, 1, Length[lk]}]

%t (* _Peter J. C. Moses_, Jan 27 2012 *)

%Y Cf. A204892.

%K nonn

%O 1,3

%A _Clark Kimberling_, Feb 01 2012

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Last modified January 18 01:05 EST 2020. Contains 330995 sequences. (Running on oeis4.)