A262375 Smallest prime factor of 4*n! - 1.
3, 3, 7, 23, 5, 479, 2879, 19, 17, 569, 14515199, 159667199, 73, 47, 61, 4993, 43, 455999, 409, 1562713, 1249, 59, 50207, 29, 71, 61651424911, 1407512357, 41, 43613, 10839629, 209206253, 47699, 3915930850588639, 12149, 337, 97, 1783, 214872195913, 89, 649849, 8405532131, 997, 53, 73, 59, 34877
Offset: 0
Keywords
Links
- Chai Wah Wu, Table of n, a(n) for n = 0..92 (n = 0..60 from Vincenzo Librandi)
Programs
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Magma
[PrimeDivisors(4*Factorial(n)-1)[1]: n in [0..50]]; // Bruno Berselli, Sep 21 2015
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Mathematica
Table[FactorInteger[4 n! - 1][[1, 1]], {n, 0, 45}] (* Michael De Vlieger, Sep 21 2015 *) -
PARI
a(n)=A020639(n!*4-1)
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PARI
a(n) = factor(4*n!-1)[1,1] \\ Michel Marcus, Sep 20 2015
Comments