A171665 Numbers n such that n and n+1 have same number of divisors, and that number of divisors is larger than 4.

44, 75, 98, 104, 116, 135, 147, 171, 189, 230, 231, 242, 243, 244, 285, 296, 332, 344, 374, 375, 387, 429, 434, 507, 548, 603, 604, 609, 645, 663, 664, 724, 735, 741, 776, 782, 805, 819, 844, 874, 902, 903, 908, 931, 963, 969, 986, 1001, 1015, 1022, 1029

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..2000

Mathematica

f[n_]:=Length[Divisors[n]]; lst={}; Do[If[f[n]==f[n+1]&&f[n]>4, AppendTo[lst, n]], {n, 7!}]; lst
Position[Partition[DivisorSigma[0, Range[1100]], 2, 1], _?(#[[1]] == #[[2]]> 4&), {1}, Heads->False]//Flatten (* Harvey P. Dale, Sep 30 2016 *)

Crossrefs

Cf. A005237

Sequence in context: A250329 A242515 A156812 * A348098 A348076 A348345

Adjacent sequences: A171662 A171663 A171664 * A171666 A171667 A171668

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Dec 14 2009

Status

approved