OFFSET
1,1
COMMENTS
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
2048 = 2^11, and both 2047 = 23*89 and 2049 = 3*683 are semiprimes.
MATHEMATICA
Select[Range[10^7], And[GCD @@ FactorInteger[#][[All, 2]] > 1, Union@ # == {2} &@ Map[PrimeOmega, {# - 1, # + 1}]] &] (* Michael De Vlieger, Dec 07 2016, after Ant King at A001597 *)
PROG
(PARI) for(i=2, 10^7, if(ispower(i)&&bigomega(i-1)==2&&bigomega(i+1)==2, print1(i, ", ")))
CROSSREFS
KEYWORD
nonn
AUTHOR
Antonio Roldán, Nov 16 2016
STATUS
approved