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 A085275 Sum of n-th composite number and its largest prime divisor. 0

%I #4 Oct 01 2013 17:57:39

%S 6,9,10,12,15,15,21,20,18,21,25,28,33,27,30,39,30,35,35,34,44,51,42,

%T 39,57,52,45,49,55,50,69,51,56,55,68,65,57,66,63,76,87,65,93,70,66,78,

%U 77,85,92,77,75,111,80,95,88,91,85,84,123,91,102,129,116,99,95,104,115,124

%N Sum of n-th composite number and its largest prime divisor.

%e For 91=7*13 we have 91+13 = 104; for 92=2*2*23 we have 92+23 = 115.

%o (PARI) cminusp3(n) = { for(x=2,n, forstep(p=x,2,-1, if(isprime(p) & x%p==0 & isprime(x)==0, print1(x+p,","); break); ) ) }

%Y Cf. A085271, A085273.

%K easy,nonn

%O 4,1

%A _Cino Hilliard_, Aug 12 2003

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Last modified May 19 19:45 EDT 2024. Contains 372703 sequences. (Running on oeis4.)