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A218164 a(n) is the smallest positive integer k such that k^64 + 1 == 0 mod p, where p is the n-th prime of the form 1 + 128*b (see A208177). 0

%I

%S 9,21,5,38,21,31,33,63,42,66,118,131,202,29,28,31,58,171,94,182,309,

%T 182,81,272,110,175,657,491,42,100,523,244,168,199,145,138,79,73,357,

%U 826,210,541,523,215,98,220,1478,22,92,178,50,709,250,2523,630,218,7

%N a(n) is the smallest positive integer k such that k^64 + 1 == 0 mod p, where p is the n-th prime of the form 1 + 128*b (see A208177).

%C A208177 : primes of the form 128*k+1.

%e a(1) = 9 because 9^64+1 = 2 * 257 * 275201 * 138424618868737 * 3913786281514524929 * 153849834853910661121 with A208177(1) = 257.

%t spi[n_]:=Module[{k=1},While[PowerMod[k,64,n]!=n-1,k++];k]; spi/@Select[128 Range[500]+1,PrimeQ] (* _Harvey P. Dale_, Jan 19 2021 *)

%Y Cf. A208177.

%K nonn

%O 1,1

%A _Michel Lagneau_, Oct 22 2012

%E Corrected by _Harvey P. Dale_, Jan 19 2021

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Last modified July 28 13:15 EDT 2021. Contains 346332 sequences. (Running on oeis4.)