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A057001 (phi(n+1)-phi(n))/2. 1
0, 1, -1, 2, -1, 1, -1, 3, -3, 4, -3, 1, 0, 4, -5, 6, -5, 2, -1, 6, -7, 6, -4, 3, -3, 8, -10, 11, -7, 2, -2, 4, -6, 12, -9, 3, -4, 12, -14, 15, -11, 2, -1, 12, -15, 13, -11, 6, -4, 14, -17, 11, -8, 6, -4, 15, -21, 22, -15, 3, -2, 8, -14, 23, -17, 6, -10, 23, -23, 24, -18, 2, -2, 12, -18, 27, -23, 11 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,4

LINKS

T. D. Noe, Table of n, a(n) for n=3..10000

MATHEMATICA

Table[(EulerPhi[n + 1] - EulerPhi[n])/2, {n, 3, 50}] (* Daniel Jolly, Nov 02 2014 *)

PROG

(MAGMA) [(EulerPhi(n + 1) - EulerPhi(n))/2: n in [3..100]]; // Vincenzo Librandi, Nov 03 2014

CROSSREFS

Cf. A000010.

Sequence in context: A079415 A126347 A309240 * A307689 A299037 A173072

Adjacent sequences:  A056998 A056999 A057000 * A057002 A057003 A057004

KEYWORD

sign

AUTHOR

N. J. A. Sloane, Sep 09 2000

STATUS

approved

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Last modified July 21 04:40 EDT 2019. Contains 325189 sequences. (Running on oeis4.)