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A023585
Least prime divisor of 2*prime(n)-1.
1
3, 5, 3, 13, 3, 5, 3, 37, 3, 3, 61, 73, 3, 5, 3, 3, 3, 11, 7, 3, 5, 157, 3, 3, 193, 3, 5, 3, 7, 3, 11, 3, 3, 277, 3, 7, 313, 5, 3, 3, 3, 19, 3, 5, 3, 397, 421, 5, 3, 457, 3, 3, 13, 3, 3, 3, 3, 541, 7, 3, 5, 3, 613, 3, 5, 3, 661, 673, 3, 17, 3, 3, 733, 5, 757, 3, 3, 13, 3, 19, 3
OFFSET
1,1
LINKS
MATHEMATICA
FactorInteger[#][[1, 1]]&/@(2Prime[Range[90]]-1) (* Harvey P. Dale, Oct 08 2017 *)
PROG
(PARI) a(n) = factor(2*prime(n)-1)[1, 1]; \\ Michel Marcus, Oct 01 2013
CROSSREFS
Sequence in context: A177904 A049072 A059887 * A089948 A336806 A023583
KEYWORD
nonn
EXTENSIONS
Definition edited by Michel Marcus, Oct 01 2013
STATUS
approved