A023585 Least prime divisor of 2*prime(n)-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

Harvey P. Dale, Table of n, a(n) for n = 1..1000

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

Cf. A020639, A076274.

Sequence in context: A177904 A049072 A059887 * A089948 A336806 A023583

Adjacent sequences: A023582 A023583 A023584 * A023586 A023587 A023588

Keyword

nonn

Author

Clark Kimberling

Extensions

Definition edited by Michel Marcus, Oct 01 2013

Status

approved