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%I
%S 2,3,31,13,71,31,19531,313,829,521,12207031,601,305175781,19531,1741,
%T 11489,466344409,5167,3981071,9161,519499,12207031,332207361361,
%U 390001,9384251,305175781,31051,234750601,22125996444329,7621
%N Largest prime factor of 5^n - 1.
%H S. S. Wagstaff, Jr., <a href="http://www.cerias.purdue.edu/homes/ssw/cun/index.html">The Cunningham Project</a>
%e 5^9 - 1 = 1953124 = (2^2)*19*31*829, so a(9) = 829.
%o (PARI) for(n=1,32, v=factor(5^n-1); print1(v[matsize(v)[1],1],","))
%Y Cf. A074478 (largest prime factor of 5^n + 1), A074477 (largest prime factor of 3^n - 1), A074249 (largest prime factor of 7^n - 1).
%K easy,nonn
%O 1,1
%A _Rick L. Shepherd_, Aug 23 2002
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