A227983 - OEIS

%I #7 Jul 25 2021 11:17:59

%S 4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,24,25,26,27,28,29,

%T 30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,48,49,50,51,52,53,

%U 54,55,56,57,58,60,61,62,63,64,65,66,67,68,69,70,71,72,73

%N Numbers n such that sigma(n+1) - sigma(n-1) < sigma(n); where sigma(n) = A000203(n) = sum of the divisors of n.

%C See A076530 - numbers n such that sigma(n+1) - sigma(n-1) = sigma(n).

%C Complement of union of A076530, A227982 and number 1.

%H Jaroslav Krizek, <a href="/A227983/b227983.txt">Table of n, a(n) for n = 1..2000</a>

%e Number 60 is in the sequence because sigma(61) - sigma(59) = 62 - 60 = 2 < sigma(60) = 168.

%t Flatten[Position[Partition[DivisorSigma[1,Range[100]],3,1],_?(#[[3]]- #[[1]]< #[[2]]&),1,Heads->False]]+1 (* _Harvey P. Dale_, Jul 25 2021 *)

%Y Cf. A076530, A000203, A227982.

%K nonn

%O 1,1

%A _Jaroslav Krizek_, Aug 08 2013