OFFSET
1,2
COMMENTS
All primes and powers of primes are necessarily in this sequence.
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1000
EXAMPLE
80 = 2^4 * 5^1 and 2+4 = 5+1, so 80 is a term.
101 = 101^1 and 101 + 1 = no other sums due to being prime, so 101 is a term.
128 = 2^7 and 2+7 = no other sums due to being a prime power, so 128 is a term.
135 = 3^3 * 5^1 and 3+3 = 5+1, so 135 is a term.
The first term with three unique prime factors is 2160 = 2^4 * 3^3 * 5^1, since 2+4 = 3+3 = 5+1.
MATHEMATICA
Join[{1}, Select[Range[2, 200], Length[Union[Plus @@@ FactorInteger[#]]] == 1 &] (* T. D. Noe, Nov 21 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Carl R. White, Nov 17 2012
STATUS
approved