A083533 First difference sequence of A002202. Difference between consecutive possible values for phi(n).

1, 2, 2, 2, 2, 2, 4, 2, 2, 2, 2, 4, 2, 2, 4, 4, 2, 2, 2, 2, 4, 2, 2, 2, 2, 4, 2, 4, 2, 6, 2, 2, 2, 4, 4, 4, 4, 2, 2, 2, 2, 2, 2, 4, 4, 6, 2, 2, 2, 4, 2, 2, 4, 4, 2, 6, 4, 2, 2, 2, 2, 4, 4, 2, 2, 4, 6, 2, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 2, 2, 4, 6, 2, 10, 2, 4, 4, 2, 2, 4, 2, 2, 4, 4, 2, 6, 4, 2, 2, 4, 6, 4, 2, 4

Offset

1,2

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Formula

a(n) = A002202(n+1) - A002202(n).

Example

12 and 16 are the 7th and 8th possible totient values 12 = phi(13), 16 = phi(17),
while {13,14,15} are impossible ones; thus 16 - 12 = 4 = a(7) = A002202(8) - A002202(7).

Mathematica

t=Table[EulerPhi[w], {w, 1, 25000}]; u=Union[%]; Delete[u-RotateRight[u], 1]

Prog

(Haskell)
a083533 n = a083533_list !! (n-1)
a083533_list = zipWith (-) (tail a002202_list) a002202_list
-- Reinhard Zumkeller, Nov 26 2015

Crossrefs

Cf. A000010, A002202, A005277, A083531, A083532, A083534, A083535, A083536, A005277.

Sequence in context: A060467 A125918 A239202 * A076500 A344887 A060594

Adjacent sequences: A083530 A083531 A083532 * A083534 A083535 A083536

Keyword

nonn

Author

Labos Elemer, May 20 2003

Status

approved