OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..2000
EXAMPLE
65 is in the sequence because 65 = 5*13, the next semiprime is 69 = 3*23, and 69-65 = 4 = 2*2, is also semiprime.
MATHEMATICA
s[n_] := PrimeOmega@n==2; L=Select[Range@910, s]; Pick[ Most@L, s /@ Differences@ L] (* Giovanni Resta, Apr 25 2016 *)
Select[Partition[Select[Range[1000], PrimeOmega[#]==2&], 2, 1], PrimeOmega[#[[2]]-#[[1]]]==2&][[All, 1]] (* Harvey P. Dale, Oct 13 2022 *)
PROG
(PARI)
proxsem(n)=local(p, s, r); s=0; p=n; while(s==0, p+=1; if(bigomega(p)==2, s=1; r=p)); p
{for(i=1, 1000, if(bigomega(i)==2, a=proxsem(i); if(bigomega(a-i)==2, print1(i, ", "))))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Antonio Roldán, Apr 25 2016
STATUS
approved