A191613 Number of even divisors of lambda(n).
0, 0, 1, 1, 2, 1, 2, 1, 2, 2, 2, 1, 4, 2, 2, 2, 4, 2, 3, 2, 2, 2, 2, 1, 4, 4, 3, 2, 4, 2, 4, 3, 2, 4, 4, 2, 6, 3, 4, 2, 6, 2, 4, 2, 4, 2, 2, 2, 4, 4, 4, 4, 4, 3, 4, 2, 3, 4, 2, 2, 8, 4, 2, 4, 4, 2, 4, 4, 2, 4, 4, 2, 9, 6, 4, 3, 4, 4, 4, 2, 4, 6, 2, 2, 4, 4, 4, 2, 6, 4, 4, 2, 4, 2, 6, 3, 10, 4, 4, 4, 6, 4, 4, 4, 4
Offset: 1
Keywords
Examples
a(13) = 4 because lambda(13) = 12 and the 4 even divisors are { 2, 4, 6, 12}.
Links
- Antti Karttunen, Table of n, a(n) for n = 1..16384
Programs
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Mathematica
f[n_] := Block[{d = Divisors[CarmichaelLambda[n]]}, Count[EvenQ[d], True]]; Table[f[n], {n, 80}] (* Second program: *) Array[DivisorSum[CarmichaelLambda@ #, 1 &, EvenQ] &, 105] (* Michael De Vlieger, Dec 04 2017 *) -
PARI
a(n) = sumdiv(lcm(znstar(n)[2]), d, 1-(d%2)); \\ Michel Marcus, Mar 18 2016
Formula
Extensions
More terms from Antti Karttunen, Dec 04 2017
Comments