A156943 - OEIS

%I #19 Oct 10 2023 09:30:39

%S 81162081,138791961,173369889,441882441,730458729,1091179089,

%T 1249127649,1524043521,1560329001,1744649361,2286465489,2606204601,

%U 3255501249,3976941969,4770526761,5567099769,6574128561,6800806089,7584145569

%N Odd abundant numbers not divisible by 25 whose abundancy is odd.

%C Number of terms < 10^n: 0, 0, 0, 0, 0, 0, 0, 1, 5, 25, 63, ..., .

%H Robert G. Wilson v, <a href="/A156943/b156943.txt">Table of n, a(n) for n=1..1005</a>

%t q[n_] := Module[{ab = DivisorSigma[1, n] - 2*n}, ab > 0 && OddQ[ab]]; Select[Range[1, 7775536039, 2], ! Divisible[#, 25] && q[#] &] (* corrected by _Amiram Eldar_, Oct 10 2023 *)

%Y Subsequence of A156903 and A156942.

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Feb 18 2009

%E Name corrected by _Amiram Eldar_, Oct 10 2023