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A105570
Nonsquarefree numbers in place: a(n) = n if n is not squarefree, 0 otherwise.
1
0, 0, 0, 0, 4, 0, 0, 0, 8, 9, 0, 0, 12, 0, 0, 0, 16, 0, 18, 0, 20, 0, 0, 0, 24, 25, 0, 27, 28, 0, 0, 0, 32, 0, 0, 0, 36, 0, 0, 0, 40, 0, 0, 0, 44, 45, 0, 0, 48, 49, 50, 0, 52, 0, 54, 0, 56, 0, 0, 0, 60, 0, 0, 63, 64, 0, 0, 0, 68, 0, 0, 0, 72, 0, 0, 75, 76, 0, 0, 0, 80, 81, 0, 0, 84, 0, 0, 0, 88, 0
OFFSET
0,5
LINKS
FORMULA
a(n) = n - abs(mu(n))*n.
Sum_{k=1..n} a(k) ~ c * n^2, where c = (1 - 1/zeta(2))/2 = 0.1960364490... . - Amiram Eldar, Feb 22 2024
MATHEMATICA
Table[If[SquareFreeQ[n], 0, n], {n, 0, 100}] (* Harvey P. Dale, Aug 13 2016 *)
PROG
(PARI) A105570(n) = if(issquarefree(n), 0, n); \\ Antti Karttunen, Jul 03 2018
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Apr 14 2005
STATUS
approved