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 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..10000 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): seq(a(n), n=1..100); # Alois P. Heinz, Feb 17 2015 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 Cf. A074206, A108501, A108502. Sequence in context: A253792 A058330 A124256 * A331595 A347288 A324213 Adjacent sequences: A108500 A108501 A108502 * A108504 A108505 A108506 KEYWORD nonn AUTHOR Christian G. Bower, Jun 06 2005 STATUS approved

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Last modified December 7 10:56 EST 2023. Contains 367650 sequences. (Running on oeis4.)