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A356207 a(n) is the difference between n! and the next smaller odd squarefree semiprime (A046388).

%I A356207 #14 Aug 29 2022 10:22:48
%S A356207 3,1,3,7,1,7,1,5,3,1,19,11,1,19,19,11,1,19,23,1,1,47,1,1,29,3,29,31,
%T A356207 59,73,1,43,1,13,17,41,1,5,5,3,53,79,7,1,53,23,1,13,13,61,7,59,61,7,
%U A356207 31,1,89,107,103,67,47,103,19,43,1,71,11,7,83,79,67,71,29
%N A356207 a(n) is the difference between n! and the next smaller odd squarefree semiprime (A046388).
%e A356207 a(4) = 3 = 4! - 3*7;
%e A356207 a(5) = 1 = 5! - 7*17;
%e A356207 a(6) = 3 = 6! - 3*239.
%o A356207 (PARI) isok(k) = my(f=factor(k)); (bigomega(f) == 2) && (omega(f)==2)
%o A356207 a(n) = my(k=n!-1); while (!isok(k), k-=2); n!-k; \\ _Michel Marcus_, Aug 29 2022
%Y A356207 Cf. A000142, A046388, A131057.
%K A356207 nonn
%O A356207 4,1
%A A356207 _Hugo Pfoertner_, Aug 28 2022
%E A356207 More terms from _Jinyuan Wang_, Aug 28 2022