OFFSET
1,2
COMMENTS
The first term is 1, since 1 has no prime factors and so the sum of prime factors evaluates to zero.
Conjecture: a(n) ~ n. - Charles R Greathouse IV, Apr 28 2015
LINKS
Hieronymus Fischer, Table of n, a(n) for n = 1..10000
EXAMPLE
a(2) = 4, since 4 = 2*2 and 2+2 = 4 is not prime.
a(5) = 14, since 14 = 2*7 and 2+7 = 9 is not prime.
MATHEMATICA
Select[Range[150], !PrimeQ[Total[Flatten[Table[#[[1]], #[[2]]]&/@ FactorInteger[ #]]]]&] (* Harvey P. Dale, Jul 05 2021 *)
PROG
(PARI) sopfr(n)=my(f=factor(n)); sum(i=1, #f~, f[i, 1]*f[i, 2])
is(n)=!isprime(sopfr(n)) \\ Charles R Greathouse IV, Apr 28 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Hieronymus Fischer, Oct 23 2007
EXTENSIONS
Edited by the author at the suggestion of T. D. Noe, May 20 2013
STATUS
approved