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A053233 Numbers n such that A053230(n) = 2.

%I A053233 #15 Oct 27 2023 22:00:45
%S A053233 3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,24,25,26,27,28,
%T A053233 29,30,33,34,35,36,37,40,41,42,43,44,45,46,47,48,49,50,51,52,53,55,56,
%U A053233 57,58,60,61,62,63,64,65,66,69,70,71,72,73,76,77,78,79,80,81,82,83,85
%N A053233 Numbers n such that A053230(n) = 2.
%H A053233 Reinhard Zumkeller, <a href="/A053233/b053233.txt">Table of n, a(n) for n = 1..10000</a>
%p A053233 with(numtheory): f := [seq( `if`((sigma(i+1) > sigma(i)),i,print( )), i=1..5000)];
%p A053233 seq( `if`(f[i+1] - f[i] = 2,i,print( )), i=1..100);
%t A053233 Position[Differences@ Select[Range[170], Less @@ DivisorSigma[1, # + {0, 1}] &], 2][[All, 1]] (* _Michael De Vlieger_, Nov 19 2019 *)
%o A053233 (Haskell)
%o A053233 import Data.List (elemIndices)
%o A053233 a053233 n = a053233_list !! (n-1)
%o A053233 a053233_list = map (+ 1) $ elemIndices 2 a053230_list
%o A053233 -- _Reinhard Zumkeller_, May 07 2012
%Y A053233 Cf. A000203, A053224, A053230, A053231, A053232, A053234, A053235, A053236, A053237.
%K A053233 nonn
%O A053233 1,1
%A A053233 _Asher Auel_, Jan 10 2000