A187562 Least k >= 0 such that prime(n)*(prime(n)-k)+1 is prime.

0, 1, 3, 1, 3, 1, 3, 7, 3, 11, 9, 3, 3, 3, 3, 9, 5, 3, 1, 11, 9, 1, 9, 5, 7, 5, 3, 9, 7, 11, 3, 21, 23, 1, 11, 1, 3, 1, 9, 3, 5, 15, 5, 1, 3, 9, 3, 13, 3, 7, 3, 5, 13, 21, 9, 21, 9, 21, 21, 5, 3, 21, 3, 3, 9, 11, 15, 1, 11, 1, 3

Offset

1,3

Links

Pierre CAMI, Table of n, a(n) for n = 1..25000

Maple

A187562 := proc(n) local p, k; p := ithprime(n) ; for k from 0 do if isprime( p*(p-k)+1 ) then return k; end if;  end do: end proc: # R. J. Mathar, Mar 13 2011

Mathematica

Table[k = 0; While[! PrimeQ[Prime[n]*(Prime[n] - k) + 1], k++]; k, {n, 100}]

Crossrefs

Sequence in context: A332031 A023511 A035628 * A370719 A057024 A023892

Adjacent sequences: A187559 A187560 A187561 * A187563 A187564 A187565

Keyword

nonn

Author

Pierre CAMI, Mar 13 2011

Status

approved