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A333261 Numbers k such that A071324(k) = A071324(k+1). 4

%I #11 Apr 04 2023 07:43:34

%S 1,5,51,68,87,116,171,176,591,2108,2403,7143,8787,9308,18548,19371,

%T 27387,32127,34887,37928,40131,140667,180548,192428,200996,433311,

%U 521727,934449,2476671,2617563,3960896,8198156,9670748,11892512,16585748,19113651,25367396,25643012

%N Numbers k such that A071324(k) = A071324(k+1).

%H Amiram Eldar, <a href="/A333261/b333261.txt">Table of n, a(n) for n = 1..89</a> (terms below 10^10)

%e 1 is a term since A071324(1) = A071324(2) = 1.

%e 5 is a term since A071324(5) = A071324(6) = 4.

%t f[n_] := Plus @@ (-(d = Divisors[n])*(-1)^(Range[Length[d],1,-1])); seq = {}; f1 = f[1]; Do[f2 = f[n]; If[f1 == f2, AppendTo[seq, n-1]]; f1 = f2, {n, 2, 50000}]; seq

%t SequencePosition[Table[Total[Times@@@Partition[Riffle[Reverse[Divisors[n]],{1,-1},{2,-1,2}],2]],{n,2565*10^4}],{x_,x_}][[All,1]] (* _Harvey P. Dale_, Nov 06 2022 *)

%Y Cf. A002961, A071324, A206368.

%K nonn

%O 1,2

%A _Amiram Eldar_, Mar 13 2020

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Last modified March 28 04:13 EDT 2024. Contains 371235 sequences. (Running on oeis4.)