OFFSET
1,1
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..10000
MATHEMATICA
Select[Prime[Range[PrimePi[5059]]], 2*DivisorSigma[0, # - 1] == DivisorSigma[0, # + 1] &] (* T. D. Noe, May 03 2011 *)
PROG
(PARI) isok(p) = isprime(p) && (numdiv(p+1) == 2*numdiv(p-1)); \\ Michel Marcus, Jan 13 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Ctibor O. Zizka, May 03 2011
STATUS
approved