OFFSET
1,3
COMMENTS
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
Colin Defant, An arithmetic function arising from the Dedekind psi function, arXiv:1501.00971 [math.NT], 2015.
FORMULA
a(1) is put to 1.
Sum_{k=1..n} a(k) ~ c * n^2, where c = 9/(2*Pi^2) = 0.4559453... (A088245). - Amiram Eldar, Nov 30 2022
MAPLE
seq(x * mul(`if`(p>2, p+1, 1)/p, p=numtheory:-factorset(x)), x = 1..100);
# Robert Israel, Jan 08 2015
MATHEMATICA
Table[If[EvenQ[n], (1/3) If[n > 1, n Times @@ (1 + 1/(Select[Divisors[n], PrimeQ])), 1], If[n > 1, n Times @@ (1 + 1/(Select[Divisors[n], PrimeQ])), 1]], {n, 260}]
PROG
(PARI) a(n)=my(f=factor(n)); prod(i=1, #f~, f[i, 1]^(f[i, 2]-1)*if(f[i, 1]>2, f[i, 1]+1, 1)) \\ Charles R Greathouse IV, Jan 08 2015
CROSSREFS
KEYWORD
nonn,mult
AUTHOR
Colin Defant, Jan 06 2015
STATUS
approved