A100363 Numbers n such that the numbers of divisors of n,n+1 and n+2 are k,2k,4k respectively for some k.

193, 397, 454, 457, 613, 614, 661, 757, 758, 997, 998, 1093, 1237, 1238, 1453, 1478, 1657, 1681, 1766, 2137, 2341, 2413, 2455, 2593, 2917, 2918, 2942, 2966, 3217, 3334, 3494, 3589, 4021, 4177, 4183, 4406, 4621, 5143, 5233, 5965, 6121, 6133, 6134, 6193

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

n=193,195,195 have 2,4,8 divisors.

Mathematica

d0[x_] :=DivisorSigma[0, x]; ta={{0}}; Do[g=n; s=d0[n]; s1=d0[n+1]; s2=d0[n+2]; If[Equal[s1, 2*s]&&Equal[s2, 4*s], ta=Append[ta, n]; Print[{n, s, s1, s2}]], {n, 1, 10000}]; {ta=Delete[ta, 1], g}
Flatten[Position[Partition[DivisorSigma[0, Range[6200]], 3, 1], _?(Length[ Union[ #/{1, 2, 4}]] == 1&), {1}, Heads->False]] (* Harvey P. Dale, Aug 03 2014 *)

Crossrefs

Cf. A000005, A063446.

Sequence in context: A256348 A142453 A065213 * A142500 A328137 A347636

Adjacent sequences: A100360 A100361 A100362 * A100364 A100365 A100366

Keyword

nonn

Author

Labos Elemer, Nov 19 2004

Status

approved