A083250 Numbers n for which abs(A045763(n) - A073757(n)) = 3, i.e., signed difference of size of related and unrelated sets to n equals either 3 or -3.

3, 825, 1755, 4641, 5313, 56865, 58395, 140049, 159152763, 361701435

Offset

1,1

Comments

No more terms below 10^9. - Amiram Eldar, Jan 27 2019

Links

Table of n, a(n) for n=1..10.

Example

For n=140049: d=40 divisors, r=70026 coprimes and u=70023 unrelated numbers to n; abs(r-u) = 3.

Mathematica

Do[r=EulerPhi[n]; d=DivisorSigma[0, n]; u=n-r-d+1; df=2*u-n; If[Equal[Abs[df], 3], Print[n(*, {d, r, u}*)]], {n, 1, 100}]

Prog

(PARI) isok(n) = abs(n-2*eulerphi(n)-2*numdiv(n)+2) == 3; \\ Michel Marcus, Jul 30 2017

Crossrefs

Cf. A000005, A000010, A045763, A073757, A083243-A083249.

Sequence in context: A293252 A341567 A287695 * A096086 A062658 A266654

Adjacent sequences: A083247 A083248 A083249 * A083251 A083252 A083253

Keyword

nonn,more

Author

Labos Elemer, May 07 2003

Extensions

a(9)-a(10) from Amiram Eldar, Jan 27 2019

Status

approved