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A171665 Numbers n such that n and n+1 have same number of divisors, and that number of divisors is larger than 4. 2

%I #7 Sep 30 2016 11:51:21

%S 44,75,98,104,116,135,147,171,189,230,231,242,243,244,285,296,332,344,

%T 374,375,387,429,434,507,548,603,604,609,645,663,664,724,735,741,776,

%U 782,805,819,844,874,902,903,908,931,963,969,986,1001,1015,1022,1029

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

%H Harvey P. Dale, <a href="/A171665/b171665.txt">Table of n, a(n) for n = 1..2000</a>

%t f[n_]:=Length[Divisors[n]]; lst={};Do[If[f[n]==f[n+1]&&f[n]>4,AppendTo[lst,n]],{n,7!}];lst

%t Position[Partition[DivisorSigma[0,Range[1100]],2,1],_?(#[[1]] == #[[2]]> 4&),{1},Heads->False]//Flatten (* _Harvey P. Dale_, Sep 30 2016 *)

%Y Cf. A005237

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Dec 14 2009

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Last modified March 2 17:35 EST 2024. Contains 370498 sequences. (Running on oeis4.)