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%I #4 Feb 11 2014 19:05:32
%S 6,907,1359,2512,26545,6094105,10714840,11967486,36282316,45123265,
%T 60144196,113547460,318424060,474656416,488176150,920250976,927186976,
%U 993590680,2509123036,3015854296,3966424141,4168017460,4360145356
%N antisigma(n) + antisigma(n+3) = antisigma(n+1) + antisigma(n+2), where antisigma(n) = sum of the non-divisors of n that are between 1 and n.
%C Each term of the sequence marks the start of four consecutive antisigma-values for which the sum of the means equals the sum of the extremes.
%e antisigma(6) + antisigma(9) = 9 + 32 = 41; antisigma(7) + antisigma(8) = 20 + 21 = 41, so 6 is a term of the sequence.
%t antisigma[n_] := (n (n + 1) / 2) - DivisorSigma[1, n]; Select[Range[10^5], antisigma[ # ] + antisigma[ # + 3] == antisigma[ # + 1] + antisigma[ # + 2] &]
%K nonn
%O 1,1
%A _Joseph L. Pe_, Oct 25 2002
%E a(6)-a(23) from _Donovan Johnson_, Dec 02 2009
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