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

Author

Vladimir Joseph Stephan Orlovsky, Dec 14 2009

Keywords

• nonn

Links

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

Crossrefs

Cf. A005237

Programs

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 *)