A088621 a(n) = smallest prime which is a concatenation of 1, n, n^2, n^3, ... n^k for some k, or 0 if no such prime exists.

11, 0, 13, 0, 0, 0, 17, 0, 19, 0, 111121, 0, 113, 0, 0, 0

Offset

1,1

Comments

a(2n)=a(5n)=0. Next term a(17) has 176 digits (k=16) and is too large to include in sequence. a(19), if it exists, has k>100. - Ray Chandler, Oct 18 2003

Links

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

Example

a(11) = 111121 which is a concatenation of 1, 11 and 121. value of k = 2.

Mathematica

f[n_] := Block[{k = FromDigits[Join[{1}, IntegerDigits[n]]], e = 1}, While[ !PrimeQ[k], e++; k = FromDigits[Join[IntegerDigits[k], IntegerDigits[n^e]]]]; k]; g[n_] := If[ Mod[n, 10] == 1 || Mod[n, 10] == 3 || Mod[n, 10] == 7 || Mod[n, 10] == 9, f[n], 0]; Table[ g[n], {n, 1, 17}] (* Robert G. Wilson v *)

Crossrefs

Cf. A088619, A068702.

Sequence in context: A055963 A127805 A256480 * A088623 A167166 A271572

Adjacent sequences: A088618 A088619 A088620 * A088622 A088623 A088624

Keyword

base,nonn

Author

Amarnath Murthy, Oct 17 2003

Status

approved