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A167350
Totally multiplicative sequence with a(p) = (p+1)*(p-2) = p^2-p-2 for prime p.
2
1, 0, 4, 0, 18, 0, 40, 0, 16, 0, 108, 0, 154, 0, 72, 0, 270, 0, 340, 0, 160, 0, 504, 0, 324, 0, 64, 0, 810, 0, 928, 0, 432, 0, 720, 0, 1330, 0, 616, 0, 1638, 0, 1804, 0, 288, 0, 2160, 0, 1600, 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) = A003959(n) * A166586(n).
Sum_{k=1..n} a(k) ~ c * n^3, where c = (2/Pi^2) / Product_{p prime} (1 + 3/p^3 + 2/p^4) = 0.1140434597... . - 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: A375992 A233807 A302771 * A215669 A244310 A334705
KEYWORD
nonn,mult
AUTHOR
Jaroslav Krizek, Nov 01 2009
STATUS
approved