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A176650 Numbers k such that nonnegative non-semiprime(k)+3 = nonnegative non-semiprime(k+3).

%I A176650 #16 Oct 15 2022 17:54:30
%S A176650 1,11,12,18,19,20,26,27,28,47,53,63,64,65,66,67,68,69,73,83,84,91,92,
%T A176650 93,98,99,100,101,102,109,115,116,117,118,122,128,129,130,134,135,136,
%U A176650 148,152,153,154,155,156,161,162,163,164,165,166,174,183,184,185,192,193
%N A176650 Numbers k such that nonnegative non-semiprime(k)+3 = nonnegative non-semiprime(k+3).
%C A176650 Where nonnegative non-semiprime numbers are zero together with A100959 (i.e., 0, 1, 2, 3, 5, 7, 8, 11, 12, 13, 16, 17, 18, 19, 20, 23, 24, 27, 28, 29, 30, ...).
%H A176650 Jinyuan Wang, <a href="/A176650/b176650.txt">Table of n, a(n) for n = 1..10000</a>
%e A176650 1 is a term because nonnegative non-semiprime(1)+3 = 3 = nonnegative non-semiprime(1+3).
%p A176650 A100959 := proc(n) option remember; if n = 1 then 1; else for a from procname(n-1)+1 do if numtheory[bigomega](a) <> 2 then return a; end if; end do end if; end proc:
%p A176650 nnnspr := proc(n) if n = 1 then 0; else A100959(n-1) ; end if; end proc:
%p A176650 isA176650 := proc(n) nnnspr(n) + 3 = nnnspr(n+3) ; end proc:
%p A176650 for n from 1 to 1200 do if isA176650(n) then printf("%d,",n) ; end if; end do:
%p A176650 # _R. J. Mathar_, Apr 26 2010
%t A176650 Join[{1},Flatten[With[{c=Select[Range[0,300],PrimeOmega[#]!=2&]},Position[ Partition [c,4,1],_?(#[[1]]+3==#[[4]]&),1,Heads->False]]]+1] (* _Harvey P. Dale_, Oct 15 2022 *)
%Y A176650 Cf. A100959 (non-semiprimes).
%K A176650 nonn
%O A176650 1,2
%A A176650 _Juri-Stepan Gerasimov_, Apr 22 2010
%E A176650 Entries checked by _R. J. Mathar_, Apr 26 2010