A089325 a(1) = 3, a(n) = smallest multiple of a(n-1) such that 10*a(n) + 1 is prime.

3, 6, 18, 54, 162, 486, 972, 1944, 5832, 40824, 204120, 408240, 816480, 1632960, 3265920, 6531840, 26127360, 130636800, 391910400, 1175731200, 14108774400, 56435097600, 1241572147200, 8691005030400, 26073015091200, 260730150912000

Offset

1,1

Links

Table of n, a(n) for n=1..26.

Example

31, 61, 181, etc. are primes.

Mathematica

k = 3; Print[k]; Do[i = 2; While[ !PrimeQ[10*i*k + 1], i++ ]; k *= i; Print[k], {n, 1, 30}] (* Ryan Propper, Aug 06 2005 *)

Crossrefs

Cf. A089326.

Sequence in context: A148564 A148565 A112572 * A110593 A049368 A152733

Adjacent sequences: A089322 A089323 A089324 * A089326 A089327 A089328

Keyword

base,nonn,easy

Author

Amarnath Murthy, Nov 03 2003

Extensions

More terms from Ryan Propper, Aug 06 2005

Status

approved