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A176512 Indices of products of 2 single (or isolated or non-twin) primes in the semiprimes.

%I A176512 #5 Feb 06 2019 23:39:03
%S A176512 1,16,25,33,35,45,52,55,58,62,76,82,84,100,104,107,111,133,137,143,
%T A176512 155,158,162,164,174,183,188,194,198,202,214,218,222,225,229,231,234,
%U A176512 241,243,249,257,263,265,269,274,281,287,292,294,299,301,304,319,320,321
%N A176512 Indices of products of 2 single (or isolated or non-twin) primes in the semiprimes.
%F A176512 A001358(k) = A176312(a(n)).
%F A176512 a(n) = A174956(A176312(n)). - _R. J. Mathar_, May 02 2010
%p A176512 From _R. J. Mathar_, May 02 2010: (Start)
%p A176512 isA007510 := proc(n) isprime(n) and not isprime(n+2) and not isprime(n-2) ; simplify(%) ; end proc:
%p A176512 isA176312 := proc(n) for d in numtheory[divisors](n) do if isA007510(d) and isA007510(n/d) then return true; end if; end do: return false; end proc:
%p A176512 A176312 := proc(n) option remember; if n = 1 then 4; else for a from procname(n-1)+1 do if isA176312(a) then return a; end if; end do: end if; end proc:
%p A176512 A174956 := proc(p) option remember ; for n from 1 do if A001358(n) = p then return n; elif A001358(n) > p then return 0 ; end if; end do: end proc:
%p A176512 A176512 := proc(n) A174956(A176312(n)) ; end proc:
%p A176512 seq(A176512(n),n=1..120) ; (End)
%K A176512 nonn
%O A176512 1,2
%A A176512 _Juri-Stepan Gerasimov_, Apr 19 2010
%E A176512 Entries checked by _R. J. Mathar_, May 02 2010