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.

1, 2, 4, 13, 6, 10, 20, 47, 22, 18, 28, 34, 51, 40, 62, 36, 30, 50, 48, 74, 42, 82, 80, 54, 105, 72, 60, 147, 78, 66, 116, 134, 84, 96, 142, 146, 108, 90, 114, 102, 172, 206, 130, 160, 226, 120, 144, 138, 126, 196, 248, 262, 162, 170, 302, 156, 186, 274, 356, 174

Offset

1,2

Links

Table of n, a(n) for n=1..60.

Example

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).

Mathematica

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

Crossrefs

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

Sequence in context: A224886 A180500 A176990 * A023640 A064454 A116662

Adjacent sequences: A109925 A109926 A109927 * A109929 A109930 A109931

Keyword

nonn

Author

Amarnath Murthy, Jul 17 2005

Extensions

More terms from T. D. Noe, Jul 17 2005

Status

approved