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A191613 Number of even divisors of lambda(n). 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Lambda is the function in A002322.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..16384

FORMULA

a(n) = A183063(A002322(n)). - Michel Marcus, Mar 18 2016

EXAMPLE

a(13) = 4 because lambda(13) = 12 and the 4 even divisors are { 2, 4, 6, 12}.

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 *)

PROG

(PARI) a(n) = sumdiv(lcm(znstar(n)[2]), d, 1-(d%2)); \\ Michel Marcus, Mar 18 2016

CROSSREFS

Cf. A002322, A183063, A193322, A193386.

Sequence in context: A324888 A249145 A048684 * A298642 A243404 A219181

Adjacent sequences:  A191610 A191611 A191612 * A191614 A191615 A191616

KEYWORD

nonn

AUTHOR

Michel Lagneau, Jul 22 2011

EXTENSIONS

More terms from Antti Karttunen, Dec 04 2017

STATUS

approved

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Last modified May 31 16:29 EDT 2020. Contains 334748 sequences. (Running on oeis4.)