|
|
A023521
|
|
Sum of distinct prime divisors of prime(n)*prime(n-1) - 1.
|
|
1
|
|
|
5, 9, 19, 21, 73, 18, 32, 111, 42, 451, 196, 381, 883, 108, 93, 526, 266, 232, 72, 2593, 36, 162, 1236, 98, 112, 752, 55, 26, 3081, 55, 4161, 1002, 9523, 135, 1616, 444, 863, 1368, 117, 415, 266, 3464, 2642, 1908, 1172, 3504, 1312, 2538, 135
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
2,1
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
|
|
MAPLE
|
p:= 2: R:= NULL:
for n from 2 to 50 do
q:= p; p:= nextprime(p);
R:= R, convert(numtheory:-factorset(p*q-1), `+`)
od:
|
|
PROG
|
(PARI) sopf(n) = my(fac=factor(n)); sum(i=1, matsize(fac)[1], fac[i, 1]) ;
a(n) = sopf(prime(n)*prime(n-1) - 1); \\ Michel Marcus, Sep 30 2013
|
|
CROSSREFS
|
|
|
KEYWORD
|
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|