OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
{ k : A178970(n) = 2 }.
MATHEMATICA
Select[Range[400], PowerMod[2, 2#-1, 2#+1]==2&] (* Harvey P. Dale, Aug 16 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Jan 05 2011
STATUS
approved