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%I #11 Oct 27 2023 22:00:45
%S 2,7,11,7,22,24,7,34,41,14,48,40,18,68,71,21,49,75,38,102,92,100,103,
%T 47,110,96,50,138,140,15,103,134,78,195,161,6,116,194,70,182,140,72,
%U 234,178,56,156,227,76,229,218,226,276,160,260,162,26,252,280,74,224
%N Second differences of sigma(n) that are positive.
%H Harvey P. Dale, <a href="/A053247/b053247.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = A053223(A053228(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 Select[Differences[DivisorSigma[1,Range[150]],2],#>0&] (* _Harvey P. Dale_, May 10 2012 *)
%Y Cf. A000203, A053223, A053248.
%K nonn
%O 1,1
%A _Asher Auel_, Jan 11 2000
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