A084701 Smallest k such that k*prime(i)-1 is prime for i = 1 to n.

2, 2, 4, 6, 120, 120, 120, 21972720, 827779590, 2481129210, 3894254360010

Offset

1,1

Comments

Perhaps a(10) = 2481129210 (from Prime Curios web page)

For n > 4, a(n) == 0 mod 30. a(10) was reported by a Prime Curios page.

Links

Table of n, a(n) for n=1..11.

Chris Caldwell, Prime Curios

Example

a(4) = 6, 2*6-1 = 11, 3*6-1 = 17, 5*6-1 = 29, 7*6-1 = 41 are all primes.

Mathematica

k = 2; Do[ While[ Union[ PrimeQ[ Table[ k*Prime[i] - 1, {i, 1, n}]]] != {True}, k+=2]; Print[k], {n, 1, 8}]

Crossrefs

Cf. A084700.

Sequence in context: A171421 A072707 A086105 * A113815 A110946 A021449

Adjacent sequences: A084698 A084699 A084700 * A084702 A084703 A084704

Keyword

more,nonn

Author

Amarnath Murthy, Jun 08 2003

Extensions

Edited and extended by Robert G. Wilson v and Don Reble, Jun 15 2003

Status

approved