OFFSET
1,1
COMMENTS
Chen semiprimes: semiprimes m such that m+4 is either a prime or a semiprime.
MAPLE
isA175634 := proc(n) isA001358(n) and (isprime(n+4) or isA001358(n+4)) ; end proc:
A175634 := proc(n) option remember; if n = 1 then 6; else for a from procname(n-1)+1 do if isA175634(a) then return a; end if; end do: end if; end proc:
isA175680 := proc(n) isA001358(n) and not isA175634(n) ; end proc:
A175680 := proc(n) option remember; if n = 1 then 4; else for a from procname(n-1)+1 do if isA175680(a) then return a; end if; end do: end if; end proc:
seq(A175735(n), n=1..120) ; # R. J. Mathar, Aug 25 2010
CROSSREFS
KEYWORD
sign,less
AUTHOR
Juri-Stepan Gerasimov, Aug 25 2010
EXTENSIONS
Keyword:sign,less set; corrected (87 replaced by 91, 210 replaced by 204) - R. J. Mathar, Aug 25 2010. Also corrected by D. S. McNeil, Aug 25 2010
STATUS
approved