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A050704
Composite numbers k with the property that k minus the sum of the prime factors of k is prime.
11
8, 9, 10, 12, 14, 15, 20, 21, 26, 28, 33, 35, 38, 39, 40, 44, 48, 51, 54, 56, 62, 65, 68, 69, 76, 77, 80, 86, 88, 91, 93, 95, 96, 111, 112, 116, 122, 123, 124, 129, 133, 136, 146, 148, 152, 159, 161, 176, 188, 189, 198, 201, 203, 206, 209, 210, 213, 215, 217, 218
OFFSET
1,1
COMMENTS
Prime factors are totaled with multiplicity, e.g., 8 = 2*2*2 so the sum of the prime factors of 8 is 6. - Harvey P. Dale, Jun 14 2011
LINKS
EXAMPLE
E.g., 161 = 7*23; 161 - (7 + 23) = 161 - 30 = 131, which is prime.
MATHEMATICA
Select[Range[250], CompositeQ[#]&&PrimeQ[#-Total[Times@@@ FactorInteger[ #]]]&] (* Harvey P. Dale, Jun 14 2011 *)
CROSSREFS
KEYWORD
nonn,nice
AUTHOR
Patrick De Geest, Aug 15 1999
STATUS
approved