A171666 Numbers n such that n, n+1 and n+2 have the same number of divisors, and that number of divisors is larger than 4.

230, 242, 243, 374, 603, 663, 902, 1105, 1274, 1309, 1334, 1832, 1885, 1924, 2013, 2054, 2133, 2264, 2343, 2504, 2523, 2665, 2696, 2936, 3110, 3655, 3656, 3729, 4203, 4401, 4503, 4504, 4614, 4669, 4695, 4807, 4923, 5133, 5862, 5943, 5944, 6054, 6061

Offset

1,1

Links

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

Mathematica

f[n_]:=Length[Divisors[n]]; lst={}; Do[If[f[n]==f[n+1]==f[n+2]&&f[n]>4, AppendTo[lst, n]], {n, 8!}]; lst
Flatten[Position[Partition[DivisorSigma[0, Range[7000]], 3, 1], _?(Length[ Union[#]]==1&&#[[1]]>4&), {1}, Heads->False]] (* Harvey P. Dale, Jul 20 2014 *)
SequencePosition[Table[If[DivisorSigma[0, n]>4, DivisorSigma[0, n], n], {n, 6100}], {x_, x_, x_}][[All, 1]] (* Harvey P. Dale, Nov 15 2021 *)

Crossrefs

Cf. A005237, A005238, A171665

Sequence in context: A072020 A177826 A122269 * A321503 A140077 A215217

Adjacent sequences: A171663 A171664 A171665 * A171667 A171668 A171669

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Dec 14 2009

Status

approved