

A108503


Number of ordered factorizations of 4*n into even numbers.


4



2, 4, 3, 8, 3, 8, 3, 16, 4, 8, 3, 20, 3, 8, 5, 32, 3, 13, 3, 20, 5, 8, 3, 48, 4, 8, 5, 20, 3, 18, 3, 64, 5, 8, 5, 38, 3, 8, 5, 48, 3, 18, 3, 20, 7, 8, 3, 112, 4, 13, 5, 20, 3, 19, 5, 48, 5, 8, 3, 56, 3, 8, 7, 128, 5, 18, 3, 20, 5, 18, 3, 104, 3, 8, 7, 20, 5, 18, 3, 112, 6, 8, 3, 56, 5, 8, 5, 48
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OFFSET

1,1


LINKS



EXAMPLE

a(9)=4 because 9*4=36 can be factored as 36=18*2=2*18=6*6.


MAPLE

with(numtheory):
b:= proc(n) option remember; 1+add(`if`(irem(d, 2)=0 and
irem(n/d, 2)=0, b(d), 0), d=divisors(n) minus {1, n})
end:
a:= n> b(4*n):


MATHEMATICA

nn = 300; f[list_, i] := list[[i]]; a = Table[Boole[EvenQ[n]], {n, 1, nn}]; Select[Map[Total, Transpose[NestList[Table[DirichletConvolve[f[#, n], f[a, n], n, m], {m, 1, nn}] &, a, nn]]], # > 1 &] (* Geoffrey Critzer, Feb 17 2015 *)


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



