A085879 - OEIS

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A085879

Smallest n-th power k^n == 1 (mod 10), where k>1.

11, 81, 1331, 81, 161051, 531441, 19487171, 6561, 2357947691, 3486784401, 285311670611, 531441, 34522712143931, 22876792454961, 4177248169415651, 43046721, 505447028499293771, 150094635296999121, 61159090448414546291, 3486784401, 7400249944258160101211, 984770902183611232881, 895430243255237372246531

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..23.

FORMULA

For n==0 (mod 4), a(n) = 3^n; for n==1,3 (mod 4), a(n) = 11^n; for n==2 (mod 4), a(n)=9^n. - Max Alekseyev, Dec 06 2013

MATHEMATICA

snp[n_]:=Module[{k=2}, While[PowerMod[k, n, 10]!=1, k++]; k^n]; Array[snp, 30] (* Harvey P. Dale, Aug 07 2023 *)

PROG

(PARI) a(n) = [3, 11, 9, 11][n%4+1]^n

CROSSREFS