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%I #21 May 27 2019 06:20:03
%S 2,6,2,2,2,2,4,2,4,2,2,16,4,8,8,4,4,8,2,16,4,2,4,16,16,4,2,4,16,8,2,
%T 16,8,16,16,48,8,4,4,8,4,8,4,4,16,8,16,16,4,16,8,8,2,16,16,32,16,8,16,
%U 16,4,8,4,16,4,8,4,64,32,32,4,8,8,32,64,8,16,16,64,16,128,8,8
%N Number of divisors of 11^n + 1 that are relatively prime to 11^m + 1 for all 0 < m < n.
%H Sean A. Irvine, <a href="/A064136/b064136.txt">Table of n, a(n) for n = 0..301</a>
%H Sam Wagstaff, Cunningham Project, <a href="https://homes.cerias.purdue.edu/~ssw/cun/">Factorizations of 11^n-1, n<=240</a>
%t a = {1}; Do[ d = Divisors[ 11^n + 1 ]; l = Length[ d ]; c = 0; k = 1; While[ k < l + 1, If[ Union[ GCD[ a, d[ [ k ] ] ] ] == {1}, c++ ]; k++ ]; Print[ c ]; a = Union[ Flatten[ Append[ a, Transpose[ FactorInteger[ 11^n + 1 ] ][ [ 1 ] ] ] ] ], {n, 0, 55} ]
%o (PARI) a(n) = if (n==0, 2, sumdiv(11^n+1, d, vecsum(vector(n-1, k, gcd(d, 11^k+1) == 1)) == n-1)); \\ _Michel Marcus_, Jun 24 2018
%Y Cf. A064131, A064132, A064133, A064134, A064135, A064137.
%K nonn,more
%O 0,1
%A _Robert G. Wilson v_, Sep 10 2001
%E a(1) corrected and more terms from _Michel Marcus_, Jul 02 2018
%E a(71)-a(82) from _Robert Price_, May 26 2019
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