OFFSET
1,3
COMMENTS
Density of nonzero terms is 0.85317570460439... = Product(1 - p^-p + p^-(p+1)) where p runs over the primes. - Charles R Greathouse IV, Jan 23 2012 [corrected by Amiram Eldar, Jan 14 2023]
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Vaclav Kotesovec, Plot of Sum_{k=1..n} a(k) / n^2 for n = 1..1000000
FORMULA
Sum_{k=1..n} a(k) ~ c * n^2, where c = (Pi^4/72) * Product_{p prime} ((1 - 1/p^5 + 2/p^4 + 2/p^3 - 4/p^2)*(1 - p - 3*p^2 + p^3 + p^4 + 2*p^(2-2*p))/(1 - p - 3*p^2 + p^3 + p^4)) = 0.2228124152... . - Amiram Eldar, Jan 14 2023
MATHEMATICA
ar[p_, s_] := Abs[p-s]; arit[1] = 1; arit[n_] := Product[ar[FactorInteger[n][[i, 1]], FactorInteger[n][[i, 2]]], {i, Length[FactorInteger[n]]}]; Array[arit, 100] (* José María Grau Ribas, Jan 25 2012 *)
PROG
(Haskell)
a203908 n = product $ map abs $
zipWith (-) (a027748_row n) (a124010_row n)
-- Reinhard Zumkeller, Dec 24 2013
CROSSREFS
KEYWORD
nonn,mult
AUTHOR
José María Grau Ribas, Jan 07 2012
STATUS
approved