OFFSET
1,2
COMMENTS
For n > 1, a(n) is an odd prime. - Chai Wah Wu, Nov 14 2022
LINKS
Remi Eismann, Table of n, a(n) for n = 1..10000
MATHEMATICA
Join[{1}, Divisors[#][[2]]&/@Range[3, 161, 2]] (* Harvey P. Dale, Oct 09 2011 *)
a[n_] := FactorInteger[2*n-1][[1, 1]]; Array[a, 80] (* Amiram Eldar, Jun 11 2022 *)
PROG
(PARI) a(n)=if(n>1, factor(2*n-1)[1, 1], 1) \\ Charles R Greathouse IV, Nov 09 2016
(Python)
from sympy import primefactors
def A090368(n): return min(primefactors((n<<1)-1), default=1) # Chai Wah Wu, Nov 14 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Lekraj Beedassy, Nov 27 2003
EXTENSIONS
More terms from Ray Chandler, Dec 02 2003
Definition corrected by Rémi Eismann, May 08 2007
STATUS
approved