OFFSET
1,3
COMMENTS
Question: With what numbers the gaps (horizontal stripes) in the scatter plot are associated? - Antti Karttunen, Jul 12 2017
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..16384
MAPLE
with(numtheory): a[1]:=0: a[2]:=1: for n from 3 to 90 do a[n]:=a[tau(n)]+a[phi(n)] od: seq(a[n], n=1..90); # Emeric Deutsch, Mar 24 2007
MATHEMATICA
f[l_List] := Block[{n = Length[l] + 1}, Append[l, l[[DivisorSigma[0, n]]] + l[[EulerPhi[n]]]]]; Nest[f, {0, 1}, 75] (* Ray Chandler, Mar 24 2007 *)
a[n_] := a[n] = If[n <= 2, n - 1, a[DivisorSigma[0, n]] + a[EulerPhi@ n]]; Array[a, 75] (* Michael De Vlieger, Jul 12 2017 *)
PROG
(PARI) A126974(n) = if(n<3, n-1, A126974(numdiv(n))+ A126974(eulerphi(n))); \\ Antti Karttunen, Jul 12 2017
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Leroy Quet, Mar 20 2007
EXTENSIONS
More terms from Emeric Deutsch and Ray Chandler, Mar 24 2007
STATUS
approved