A076485 Solutions to gcd(sigma(x), phi(x)) > gcd(sigma(core(x)), phi(core(x))), i.e., when A009223(x) > A066086(x) or if A066087(x) > 0.

12, 18, 24, 44, 48, 49, 54, 56, 72, 88, 92, 96, 99, 108, 112, 116, 125, 132, 135, 140, 147, 152, 162, 168, 169, 172, 176, 184, 188, 192, 196, 198, 200, 207, 216, 224, 236, 248, 250, 264, 270, 276, 280, 284, 288, 297, 308, 328, 332, 336, 344, 348, 352, 361

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

For n=12: sigma(12)=28, phi(12)=4, gcd(28,4)=4 core(12)=6, sigma(6)=12, phi(6)=2, gcd(12,2)=2.

Mathematica

ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] cor[x_] := Apply[Times, ba[x]] g1[x_] := GCD[DivisorSigma[1, x], EulerPhi[x]] g2[x_] := GCD[DivisorSigma[1, cor[x]], EulerPhi[cor[x]]] Do[s1=g1[n]; s2=g2[n]; If[Greater[s1, s2], Print[n]], {n, 1, 256}]

Crossrefs

Cf. A000010, A000203, A007947, A009223, A023900, A048250, A066086, A066087.

Sequence in context: A245379 A363814 A224218 * A325387 A272860 A071354

Adjacent sequences: A076482 A076483 A076484 * A076486 A076487 A076488

Keyword

nonn

Author

Labos Elemer, Oct 17 2002

Status

approved