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A078119 sigma(n) - phi(n+2), where sigma = sum of divisors (A000203) and phi = Euler totient function (A000010). 1
-1, 1, 0, 5, 0, 8, 2, 11, 3, 14, 0, 22, 6, 16, 8, 25, 0, 31, 8, 32, 10, 28, 4, 48, 13, 30, 12, 48, 0, 56, 12, 47, 24, 42, 12, 73, 14, 44, 16, 78, 0, 76, 20, 62, 32, 56, 6, 104, 25, 69, 20, 80, 14, 96, 36, 92, 22, 74, 0, 138, 26, 64, 56, 107, 18, 112, 24, 102, 26, 120, 0, 159, 34, 78, 64, 116, 18 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
For n>1: a(n)>=0 and a(n)=0 iff (n,n+2) is a twin prime pair.
LINKS
MATHEMATICA
Table[DivisorSigma[1, n]-EulerPhi[n+2], {n, 80}] (* Harvey P. Dale, Dec 25 2012 *)
PROG
(PARI) a(n)=sigma(n)-eulerphi(n+2) \\ Charles R Greathouse IV, Feb 19 2013
CROSSREFS
Sequence in context: A199376 A011510 A021667 * A085998 A094886 A143821
KEYWORD
sign
AUTHOR
Reinhard Zumkeller, Dec 06 2002
STATUS
approved

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Last modified March 3 04:18 EST 2024. Contains 370499 sequences. (Running on oeis4.)