OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1)=5 because p_1+p_2=2+3=5, and sopfr(5)=5
a(2)=6 because p_2+p_3=3+5==2*2*2, and sopfr(8)=2+2+2=6
a(4)=8 because p_4+p_5=7+11=18=2*3*3 and sopfr(18)=2+3+3=8.
MAPLE
spf:= n -> add(t[1]*t[2], t=ifactors(n)[2]):
P:= [seq(ithprime(i), i=1..101)]:
map(spf, P[2..-1]+P[1..-2]); # Robert Israel, Nov 19 2020
MATHEMATICA
spf[n_]:=Total[Flatten[Table[#[[1]], #[[2]]]&/@FactorInteger[n]]]; Module[ {tsp=Total/@Partition[Prime[Range[80]], 2, 1]}, spf/@tsp] (* Harvey P. Dale, Jul 12 2020 *)
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Zak Seidov, Jul 29 2009
STATUS
approved