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A053248 Second differences of sigma(n) that are negative. 2

%I #9 Oct 27 2023 22:00:45

%S 1,4,10,9,11,30,10,20,40,32,16,65,13,42,82,46,12,96,26,82,106,46,18,

%T 143,57,70,114,88,40,214,26,66,136,88,120,244,30,60,160,171,47,256,36,

%U 150,266,96,40,286,88,176,226,124,12,24,342,170,230,222,94,34,443,71

%N Second differences of sigma(n) that are negative.

%F a(n) = A053223(A053229(n)).

%p with (numtheory): f := [seq( sigma(i+2) - sigma(i+1) - (sigma(i+1) - sigma(i)), i=1..200)];

%p seq(`if`(f[i] < 0,f[i],print( )), i=1..200);

%t Abs[Select[Differences[DivisorSigma[1,Range[200]],2],Negative]] (* _Harvey P. Dale_, Aug 13 2015 *)

%Y Cf. A000203, A053223, A053247.

%K nonn

%O 1,2

%A _Asher Auel_, Jan 11 2000

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Last modified June 12 18:49 EDT 2024. Contains 373359 sequences. (Running on oeis4.)