OFFSET
1,1
COMMENTS
From an idea of Michael B. Porter.
LINKS
Paolo P. Lava, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
prime(8) = 19, and 19+1 = 20 = 2*2*5, so a(8) = 2+2+5 = 9.
MAPLE
with(numtheory);
P:=proc(i)
local a, k, n;
for n from 1 to i do
a:=ifactors(ithprime(n)+1)[2]; print(add(a[k][1]*a[k][2], k=1..nops(a)));
od; end:
# alternative
A210934 := proc(n)
local p, pplus, f ;
p := ithprime(n) ;
pplus := ifactors(p+1)[2] ;
add(op(1, f)*op(2, f), f=pplus) ;
end proc:
seq(A210934(n), n=1..300) ; # R. J. Mathar, May 25 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Mar 30 2012
STATUS
approved