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 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. 0
 11, 0, 13, 0, 0, 0, 17, 0, 19, 0, 111121, 0, 113, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified June 18 12:00 EDT 2024. Contains 373481 sequences. (Running on oeis4.)