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A083251 Numbers n such that abs(A045763(n) - A073757(n)) = 2, i.e., signed difference of size of related and unrelated sets to n equals either 2 or -2. 3
2, 48, 72, 80, 112, 176, 208, 272, 304, 368, 464, 496, 592, 656, 688, 752, 848, 944, 976, 1072, 1136, 1168, 1264, 1328, 1424, 1552, 1616, 1648, 1712, 1744, 1808, 2032, 2096, 2192, 2224, 2384, 2416, 2512, 2608, 2672, 2768, 2864, 2896 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
a(n) = 8 * (A076274(n-1) + 1) for n > 3, as proved by Lawrence Sze. - Ralf Stephan, Nov 16 2004
EXAMPLE
For n=2896: d=10 divisors, r=1440 coprimes, u=1447 unrelated or n - u = r + d - 1 = 1449 related numbers to n; thus abs(1449 - 1447) = 2.
MATHEMATICA
Do[r=EulerPhi[n]; d=DivisorSigma[0, n]; u=n-r-d+1; df=2*u-n; If[Equal[Abs[df], 2], Print[n(*, {d, r, u}*)]], {n, 1, 3000}]
CROSSREFS
Sequence in context: A087259 A195876 A326778 * A226401 A226396 A341110
KEYWORD
nonn
AUTHOR
Labos Elemer, May 07 2003
STATUS
approved

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Last modified March 28 04:13 EDT 2024. Contains 371235 sequences. (Running on oeis4.)