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A108607 4-almost primes whose sum of factors is a prime. 5

%I #7 Oct 11 2013 12:12:34

%S 40,54,56,88,90,104,136,184,198,210,248,250,294,296,328,350,376,390,

%T 414,424,462,488,522,536,550,570,584,664,686,714,776,798,808,824,850,

%U 856,858,930,950,954,1014,1048,1062,1110,1190,1208,1210,1218,1256,1274,1278

%N 4-almost primes whose sum of factors is a prime.

%H Charles R Greathouse IV, <a href="/A108607/b108607.txt">Table of n, a(n) for n = 1..10000</a>

%e 40=2*2*2*5 (4-almost prime) and 2+2+2+5=11 is a prime.

%o (PARI) is(n)=my(f=factor(n));sum(i=1,#f~,f[i,2])==4 && isprime(sum(i=1,#f~,f[i,1]*f[i,2])) \\ _Charles R Greathouse IV_, Oct 11 2013

%Y Cf. A107707, A108608, A108609 (resp.) 3, 5, 6 (resp.)-almost primes whose sum of factors is a prime.

%K nonn

%O 1,1

%A _Zak Seidov_, Jun 12 2005

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Last modified March 28 14:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)