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A109928 Least k such that there are n primes of the form kr+1 with 1<=r<=k. Index of the first occurrence of n in A085053. 0

%I

%S 1,2,4,13,6,10,20,47,22,18,28,34,51,40,62,36,30,50,48,74,42,82,80,54,

%T 105,72,60,147,78,66,116,134,84,96,142,146,108,90,114,102,172,206,130,

%U 160,226,120,144,138,126,196,248,262,162,170,302,156,186,274,356,174

%N Least k such that there are n primes of the form kr+1 with 1<=r<=k. Index of the first occurrence of n in A085053.

%e a(6) = 10 as 10 is the least number that gives 6 primes of the form 10k +1, k<=10. (11,31,41,61,71,101).

%t t=Table[Length[Select[Range[n], PrimeQ[n#+1]&]], {n, 1000}]; Table[First[Flatten[Position[t, n]]], {n, 100}] (Noe)

%Y Cf. A085053 (number of primes of the form kn+1, with k<=n).

%K nonn

%O 1,2

%A _Amarnath Murthy_, Jul 17 2005

%E More terms from _T. D. Noe_, Jul 17 2005

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Last modified June 15 15:16 EDT 2021. Contains 345049 sequences. (Running on oeis4.)