OFFSET
1,4
REFERENCES
B. B. Mandelbrot, The Fractal Geometry of Nature, Freeman, NY, 1982, p. 183.
R. Penrose, The Emperor's New Mind, Penguin Books, NY, 1991, p. 138.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Cheng Zhang, Table of n, a(n) for n = 1..1000
R. P. Munafo, Enumeration of Features
FORMULA
a(n) = 2*l(n) - sum_{d|n} phi(n/d)*l(d), where l(n) = sum_{d|n} mu(n/d) 2^(d-1) (A000740), and phi(n) and mu(n) are the Euler totient function (A000010) and Moebius function (A008683), respectively. - Cheng Zhang, Apr 02 2012
MATHEMATICA
degRp[n_] := Sum[MoebiusMu[n/d] 2^(d - 1), {d, Divisors[n]}]; Table[degRp[n]*2 - Sum[EulerPhi[n/d] degRp[d], {d, Divisors[n]}], {n, 1, 100}] (* Cheng Zhang, Apr 02 2012 *)
PROG
(PARI) A000740(n)=sumdiv(n, d, moebius(n/d)<<(d-1))
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
EXTENSIONS
Web link changed to more relevant page by Robert Munafo, Nov 16 2010
More terms from Cheng Zhang, Apr 02 2012
STATUS
approved