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A167345
Totally multiplicative sequence with a(p) = (p-1)*(p-2) = p^2-3p+2 for prime p.
1
1, 0, 2, 0, 12, 0, 30, 0, 4, 0, 90, 0, 132, 0, 24, 0, 240, 0, 306, 0, 60, 0, 462, 0, 144, 0, 8, 0, 756, 0, 870, 0, 180, 0, 360, 0, 1260, 0, 264, 0, 1560, 0, 1722, 0, 48, 0, 2070, 0, 900, 0
OFFSET
1,3
LINKS
FORMULA
Multiplicative with a(p^e) = ((p-1)*(p-2))^e. If n = Product p(k)^e(k) then a(n) = Product ((p(k)-1)*(p(k)-2))^e(k).
a(2k) = 0 for k >= 1.
a(n) = A003958(n) * A166586(n).
Sum_{k=1..n} a(k) ~ c * n^3, where c = (2/Pi^2) / Product_{p prime} (1 + 2/p^2 + 1/p^3 - 2/p^4) = 0.090842681006... . - Amiram Eldar, Dec 15 2022
MATHEMATICA
a[1] = 1; a[n_] := (fi = FactorInteger[n]; Times @@ ((fi[[All, 1]] - 1)^fi[[All, 2]])); b[1] = 1; b[n_] := (fi = FactorInteger[n]; Times @@ ((fi[[All, 1]] - 2)^fi[[All, 2]])); Table[a[n]*b[n], {n, 1, 100}] (* G. C. Greubel, Jun 10 2016 *)
CROSSREFS
Sequence in context: A053814 A293260 A095238 * A292496 A285480 A156431
KEYWORD
nonn,mult
AUTHOR
Jaroslav Krizek, Nov 01 2009
STATUS
approved