A261890 - OEIS

%I #8 Mar 12 2023 13:34:02

%S 2,4,-8,16,-24,20,-7,10,-31,32,-24,40,-26,-16,-2,34,-36,38,2,-20,-46,

%T 68,-23,26,-52,26,-29,28,0,32,2,-32,0,-36,-2,112,-74,-40,-2,40,0,44,

%U -43,46,-139,140,-47,0,51,-102,-2,106,2,-110,112,-56,-118,176,-120

%N Second differences of A055615, first differences of A261869.

%C a(n) = (n+2)*mu(n+2) - 2*(n+1)*mu(n+1) + n*mu(n), where mu = A008683 (Moebius function);

%C a(A114180(n)) = 0;

%C abs(a(n)) <= 4*(n+1).

%H Reinhard Zumkeller, <a href="/A261890/b261890.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A055615(n+2) - 2*A055615(n+1) + A055615(n).

%t Differences[Table[n MoebiusMu[n],{n,80}],2] (* _Harvey P. Dale_, Mar 12 2023 *)

%o (Haskell)

%o import Data.List (genericIndex)

%o a261890 n = genericIndex a261890_list (n - 1)

%o a261890_list = zipWith (-) (tail a261869_list) a261869_list

%Y Cf. A008683, A055615, A261869, A114180.

%K sign

%O 1,1

%A _Reinhard Zumkeller_, Sep 05 2015