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A210936 Sum of prime factors of prime(n)-1 (counted with multiplicity). 4
0, 2, 4, 5, 7, 7, 8, 8, 13, 11, 10, 10, 11, 12, 25, 17, 31, 12, 16, 14, 12, 18, 43, 17, 13, 14, 22, 55, 13, 15, 15, 20, 23, 28, 41, 15, 20, 14, 85, 47, 91, 15, 26, 15, 18, 19, 17, 42, 115, 26, 35, 26, 16, 17, 16, 133, 71, 16, 30, 18, 52, 77, 25, 38, 22, 83 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
From an idea of Michael B. Porter.
LINKS
FORMULA
a(n) = A001414(A006093(n)). - Michel Marcus, Oct 05 2013
EXAMPLE
prime(10) = 29, and 29-1 = 28 = 2*2*7, so a(10) = 2+2+7 = 11.
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
A210936 := 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(A210936(n), n=1..300) ; # R. J. Mathar, May 25 2022
CROSSREFS
Sequence in context: A224367 A308219 A288758 * A140203 A085888 A329531
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Mar 30 2012
STATUS
approved

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Last modified March 19 01:57 EDT 2024. Contains 370952 sequences. (Running on oeis4.)