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%I #4 Mar 30 2012 18:40:02
%S 2,0,2,3,0,2,0,0,2,3,2,0,0,2,5,0,3,2,0,2,0,0,0,3,0,0,2,0,2,3,0,2,7,5,
%T 0,2,3,0,2,0,0,2,0,3,2,0,0,2,0,0,3,0,5,2,0,0,2,3,0,2,0,0,0,2,3,0,2,0,
%U 0,0,2,7,3,5,0,2,0,0,3,0,0,2,0,0,2,3,0,0,2,11,0,0,2,5,3,2,0,0,2,0,0,3
%N Largest prime factor of prime power > 1 that divides the n-th composite number; or a(n) = 0 iff n-th composite number is equal to the product of distinct primes.
%e a(6) = 2 because C(6) = 12 = 3*2^2 and the largest prime factor of power 2^2 is 2.
%e a(28) = 0 because C(28) = 42 = 2*3*7 is the product of distinct primes
%o (PARI) A002808(n)={for(k=0,primepi(n),isprime(n++)&k--);n} A111565(n)={local(f,r,i);f=factor(A002808(n));r=0;i=matsize(f)[1];while((r==0)&&(i>0),if(f[i,2]>1,r=f[i,1],i--));r}
%Y Cf. A002808 (composite numbers)
%K nonn
%O 1,1
%A _Giovanni Teofilatto_, Nov 17 2005
%E a(28) changed by _Michael B. Porter_, Feb 02 2010
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