A083250 - OEIS

A083250

Numbers m for which abs(A045763(m) - A073757(m)) = 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, 104779406861402235, 1629670195756850430465

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OFFSET

1,1

LINKS

EXAMPLE

For m=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

KEYWORD

nonn,more

AUTHOR

Labos Elemer, May 07 2003

EXTENSIONS

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

a(11)-a(12) from Max Alekseyev, Nov 13 2025

STATUS

approved