A337429 a(n) is the largest prime factor of 2^n + 5^n.
2, 7, 29, 19, 641, 41, 541, 1597, 22993, 397, 5521, 303293, 380881, 25117, 210466621, 508771, 1573071713, 108991369171, 1343341, 2724783836059, 39558401, 2525293, 4807441, 215038823, 1173553, 61001, 16463734208221, 3813697527769, 58116853330557841, 327866809, 99901
Offset: 0
Keywords
Links
- Amiram Eldar, Table of n, a(n) for n = 0..387 (terms 0..200 from Hugo Pfoertner)
Programs
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Mathematica
a[n_] := FactorInteger[2^n + 5^n][[-1, 1]]; Array[a, 31, 0] (* Amiram Eldar, Mar 30 2023 *)
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PARI
for(n=0,30,my(p=2^n+5^n);print1(vecmax(factor(p)[,1]),", "))