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A181835
The sum of the primes <= n that are strongly prime to n.
9
0, 0, 0, 0, 0, 3, 0, 5, 8, 12, 7, 10, 12, 23, 19, 24, 31, 39, 36, 53, 51, 60, 54, 64, 72, 90, 80, 82, 88, 91, 90, 119, 127, 144, 127, 129, 143, 155, 139, 160, 174, 190, 185, 226, 225, 260, 248, 256
OFFSET
0,6
COMMENTS
k is strongly prime to n iff k is relatively prime to n and k does not divide n-1.
EXAMPLE
a(11) = 3 + 7 = 10.
MAPLE
with(numtheory):
Primes := n -> select(k->isprime(k), {$1..n}):
StrongCoprimes := n -> select(k->igcd(k, n)=1, {$1..n}) minus divisors(n-1):
StrongCoprimePrimes := n -> Primes(n) intersect StrongCoprimes(n):
A181835 := proc(n) local i; add(i, i=StrongCoprimePrimes(n)) end:
MATHEMATICA
a[n_] := Select[Range[2, n], PrimeQ[#] && CoprimeQ[#, n] && !Divisible[n-1, #] &] // Total; Table[a[n], {n, 0, 47}] (* Jean-François Alcover, Jun 28 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Nov 17 2010
STATUS
approved