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

40, 54, 56, 88, 90, 104, 136, 184, 198, 210, 248, 250, 294, 296, 328, 350, 376, 390, 414, 424, 462, 488, 522, 536, 550, 570, 584, 664, 686, 714, 776, 798, 808, 824, 850, 856, 858, 930, 950, 954, 1014, 1048, 1062, 1110, 1190, 1208, 1210, 1218, 1256, 1274, 1278

Offset: 1

Author

Zak Seidov, Jun 12 2005

Keywords

• nonn

Examples

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

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

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

Programs

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