A244149 - OEIS

%I #42 Feb 26 2025 02:00:09

%S 1,1,1,3,1,5,1,7,5,9,1,11,1,13,9,15,1,17,1,19,13,21,1,23,9,25,17,3,1,

%T 29,1,31,21,33,69,35,1,37,25,39,1,41,1,43,5,45,1,47,13,49,33,51,1,53,

%U 109,55,37,57,1,59,1,61,41,63,25,65,1,67,45,9,1,71,1,73,49,75,153,77,1,79

%N a(n) = 2*(n*denominator(((n-1)*(n^2)+2^(n+1)-4)/(2*n))-n)/n+1.

%H Antti Karttunen, <a href="/A244149/b244149.txt">Table of n, a(n) for n = 1..20000</a>

%e a(1) = 2*(1*denominator(((1-1)*(1^2)+2^(1+1)-4)/(2*1))-1)/1+1 = 1.

%t A244149[n_] := 2*(n*Denominator[((n-1)*n^2 + 2^(n+1) - 4)/(2*n)] - n)/n + 1;

%t Array[A244149, 100] (* _Paolo Xausa_, Jan 27 2025 *)

%o (Magma) [2*(n*Denominator(((n-1)*(n^2)+2^(n+1)-4)/(2*n))-n)/n+1: n in [1..100]];

%o (PARI) a(n) = 2*(n*denominator(((n-1)*(n^2)+2^(n+1)-4)/(2*n))-n)/n + 1; \\ _Michel Marcus_, Sep 03 2014

%Y Cf. A000040, A001567, A015919, A065091.

%K nonn,changed

%O 1,4

%A _Juri-Stepan Gerasimov_, Sep 01 2014