A185026 The first bisection of the sequence A002616 of reduced totients.

1, 2, 3, 3, 5, 6, 2, 8, 9, 3, 11, 10, 9, 14, 15, 5, 6, 18, 6, 20, 21, 6, 23, 21, 8, 26, 10, 9, 29, 30, 3, 6, 33, 11, 35, 36, 10, 15, 39, 27, 41, 8, 14, 44, 6, 15, 18, 48, 15, 50, 51, 6, 53, 54, 18, 56, 22, 6, 24, 55, 20, 50, 63, 21, 65, 9, 18, 68, 69, 23, 30, 14, 21, 74, 75, 24, 30, 78, 26, 33

Offset: 1

Author

Paul Curtz, Dec 24 2012

Keywords

• nonn

Comments

Fixed points n where n=a(n) are n=1, 2, 3, 5, 6, 8, 9, 11,... = A005097.

There are pairs of the consecutive terms of the form (3*k,k): 6,2, 9,3, 15,5, 18,6, 33,11, 54,18, 63,21, 69,23, 78,26, ... . It seems that k is the set of all A174100(n), n>1, plus a few exceptions (like the pair 126, 42).

Links

• G. C. Greubel, Table of n, a(n) for n = 1..5000

Programs

Maple

A185026 := proc(n)
        numtheory[lambda](2*n+1)/2 ;
end proc: # R. J. Mathar, Mar 27 2013

Mathematica

Table[ CarmichaelLambda[2*n + 1]/2, {n, 1, 80}] (* Jean-François Alcover, Apr 04 2013 *)

Formula

a(n) = A002616(2*n+1).