A002616 Reduced totient function (divided by 2).

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

Offset: 3

Author

N. J. A. Sloane

Keywords

• nonn
• easy

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.

Crossrefs

Cf. A002322.

Programs

Haskell

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

Mathematica

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

PARI

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

Formula

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

Extensions

More terms from Vladeta Jovovic, Apr 04 2002