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A141553 Transformed nonprime products of prime factors of the composites, the largest prime decremented by 2 and the smallest prime incremented by 1. 1

%I

%S 0,0,4,9,6,15,12,0,9,18,20,27,12,18,33,12,30,27,0,36,45,30,18,51,44,

%T 36,45,54,36,63,24,40,45,60,66,27,54,60,68,81,54,87,60,0,66,81,90,84,

%U 75,36,105,60,102,72,99,72,36,117,90,90,123,108,108,81,88,126,116,135,102,48

%N Transformed nonprime products of prime factors of the composites, the largest prime decremented by 2 and the smallest prime incremented by 1.

%C In the prime number decomposition of k=A002808(i), i=1,2,3,.., one instance of the largest prime, pmax=A052369(i), is replaced by pmax-2 and one instance of the smallest prime, pmin=A056608(i), is replaced by pmin+1. If the product of this modified list of factors, k*(pmax-2)*(pmin+1)/(pmin*pmax), is nonprime, it is added to the sequence.

%e k(1)=(p(max)=2)*(p(min)=2), transformed (2-2)*(2+1)=0*3=0=a(1).

%e k(2)=(p(max)=3)*(p(min)=2), transformed (3-2)*(2+1)=1*3=3 (prime, skipped).

%e k(3)=(p(max)=2)*(p=2)*(p(min)=2), transformed (2-2)*2*(2+1)=0*2*3=0=a(2), etc.

%Y Cf. A141218, A141219, A141220, A141284.

%K nonn

%O 1,3

%A _Juri-Stepan Gerasimov_, Aug 14 2008

%E Edited and corrected by _R. J. Mathar_, Aug 18 2008

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Last modified August 7 17:44 EDT 2020. Contains 336278 sequences. (Running on oeis4.)