A172130 a(n) = the smallest k such that n(n+1)(n+2)...(n+k-1)-1 is a prime

3, 2, 1, 1, 2, 1, 3, 1, 2, 2, 2, 1, 2, 1, 2, 2, 3, 1, 2, 1, 2, 3, 3, 1, 17, 2, 4, 2, 6, 1, 2, 1, 10, 3, 2, 9, 3, 1, 2, 3, 2, 1, 4, 1, 2, 2, 3, 1, 4, 2, 8, 7, 2, 1, 2, 2, 3, 3, 2, 1, 11, 1, 3, 2, 2, 2, 5, 1, 3, 2, 11, 1, 4, 1, 3, 2, 7, 7, 5, 1, 4, 38, 2, 1, 2, 2, 7, 9, 2, 1, 4, 4, 2, 2, 4, 2, 3, 1, 14, 2, 2, 1, 2

Offset

1,1

Comments

a(534) = 624 is particularly large.

Links

Table of n, a(n) for n=1..103.

Mathematica

a[n_] := Block[{}, For[s = n; k = 1, ! PrimeQ[s - 1], s *= n + k; k++ ]; k]; Table[a[n], {n, 1, 300}]

Crossrefs

Cf. A172125, A172133, A087564

Sequence in context: A247044 A083663 A085427 * A202449 A326613 A288627

Adjacent sequences: A172127 A172128 A172129 * A172131 A172132 A172133

Keyword

nonn

Author

Cheng Zhang (cz1(AT)rice.edu), Jan 26 2010, Mar 03 2010

Status

approved