OFFSET
1,1
COMMENTS
The subsequence of prime terms is A005478; a term is prime if and only if it is a Fibonacci prime (proved by Giovanni Resta).
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..51
FORMULA
EXAMPLE
a(3)=5 since 5 is the smallest number whose sum of prime divisors is soprf(2) + sopfr(3) = 2 + 3 = 5. a(4)=15 since sopfr(3)+sopfr(5)=8, and 15 is the smallest number whose sum of prime divisors is 8.
MATHEMATICA
sopfr[n_] := Plus @@ Times @@@ FactorInteger[n]; a[1] = 2; a[2] = 3; a[n_] := a[n] = Block[{t = sopfr@ a[n-1] + sopfr@ a[n-2], k=3}, While[ sopfr[k] != t, k++]; k]; Array[a, 21] (* Giovanni Resta, Jan 07 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
David James Sycamore, Jan 05 2020
STATUS
approved