A109947 Smallest prime == 1 (mod f(n)), where f(n) = concatenation 1,2,3,... up to n.

2, 13, 739, 4937, 24691, 123457, 29629609, 24691357, 1234567891, 530864193131, 12345678910111, 1851851836516681, 74074073460667279, 76543209242689521469, 8395061658875624936221, 123456789101112131415161

Offset

1,1

Links

Table of n, a(n) for n=1..16.

Mathematica

s = "1"; Do[s = s <> ToString[n]; k = ToExpression[s]; i = 1; While[ !PrimeQ[i*k + 1], i++ ]; Print[i*k + 1], {n, 2, 30}] (* Ryan Propper, Aug 01 2005 *)

Crossrefs

Cf. A109948.

Sequence in context: A179434 A101342 A119122 * A175513 A064185 A069109

Adjacent sequences: A109944 A109945 A109946 * A109948 A109949 A109950

Keyword

base,nonn

Author

Amarnath Murthy, Jul 20 2005

Extensions

More terms from Ryan Propper, Aug 01 2005

Status

approved