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A193525 Number of even divisors of sopf(n). 2
0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 3, 1, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 1, 2, 0, 4, 0, 0, 0, 4, 0, 0, 4, 0, 0, 3, 0, 0, 0, 0, 0, 4, 0, 0, 0, 4, 0, 2, 0, 0, 2, 0, 0, 2, 1, 3, 4, 0, 0, 2, 2, 0, 0, 0, 0, 3, 0, 3, 3, 0, 0, 0, 0, 0, 4, 2, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,15

COMMENTS

Sopf(n) is the sum of the distinct primes dividing n (A008472).

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

a(15) = 3 because sopf(15) = 8 and its 3 even divisors are {2, 4, 8}.

MATHEMATICA

f[n_] := Block[{d=Divisors[Plus@@First[Transpose[FactorInteger[n]]]]}, Count[EvenQ[d], True]]; Table[f[n] , {n, 100}]

PROG

(PARI) sopf(n:int)=my(f=factor(n)[, 1]); sum(i=1, #f, f[i])

a(n)=if(n==1, 0, n=sopf(n); if(n%2, 0, numdiv(n/2))) \\ Charles R Greathouse IV, Jul 31 2011

CROSSREFS

Cf. A008472.

Sequence in context: A180017 A243827 A059530 * A049828 A286131 A285631

Adjacent sequences:  A193522 A193523 A193524 * A193526 A193527 A193528

KEYWORD

nonn

AUTHOR

Michel Lagneau, Jul 29 2011

STATUS

approved

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Last modified March 18 22:11 EDT 2019. Contains 321305 sequences. (Running on oeis4.)