A002616 - OEIS

A002616

Reduced totient function (divided by 2).
(Formerly M0128 N0052)

1, 1, 2, 1, 3, 1, 3, 2, 5, 1, 6, 3, 2, 2, 8, 3, 9, 2, 3, 5, 11, 1, 10, 6, 9, 3, 14, 2, 15, 4, 5, 8, 6, 3, 18, 9, 6, 2, 20, 3, 21, 5, 6, 11, 23, 2, 21, 10, 8, 6, 26, 9, 10, 3, 9, 14, 29, 2, 30, 15, 3, 8, 6, 5, 33, 8, 11, 6, 35, 3, 36, 18, 10, 9, 15, 6, 39, 2, 27, 20, 41, 3, 8, 21, 14, 5, 44, 6, 6

(list; graph; refs; listen; history; text; internal format)

OFFSET

3,3

COMMENTS

A046073 is a similar sequence (the first difference occurs at position 61). - Artur Jasinski, Apr 05 2008

REFERENCES

D. H. Lehmer, Guide to Tables in the Theory of Numbers. Bulletin No. 105, National Research Council, Washington, DC, 1941, pp. 7-10.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 3..1000

A. Cauchy, Mémoire sur la résolution des équations indéterminées du premier degré en nombres entiers, Oeuvres Complètes. Gauthier-Villars, Paris, 1882-1938, Series (2), Vol. 12, pp. 9-47.

FORMULA

a(n) = A002322(n)/2.

MATHEMATICA

Table[CarmichaelLambda[k + 2]/2, {k, 130}] (* Artur Jasinski, Apr 05 2008 *)

PROG

(Haskell)

a002616 = flip div 2 . a002322 -- Reinhard Zumkeller, Sep 02 2014

(PARI) a(n) = lcm(znstar(n)[2])/2; \\ Michel Marcus, May 22 2022

CROSSREFS

Cf. A002322.

Sequence in context: A075825 A309155 A007735 * A046073 A309786 A162912

Adjacent sequences: A002613 A002614 A002615 * A002617 A002618 A002619