OFFSET
1,1
COMMENTS
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
a(4)=46 because 46 is the 4th semiprime such that 2*46+1=93 is a semiprime and both of its factors are Sophie Germain primes: 2*2+1=5 and 2*23+1=47.
MATHEMATICA
seqQ[n_] := AllTrue[{n, 2*n + 1}, PrimeOmega[#] == 2 &] && AllTrue[First /@ FactorInteger[n], PrimeQ[2*# + 1] &]; Select[Range[3000], seqQ] (* Amiram Eldar, May 10 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Christopher M. Tomaszewski (cmt1288(AT)comcast.net), Oct 24 2005
EXTENSIONS
Extended by Ray Chandler, Oct 31 2005
STATUS
approved