A160257 - OEIS

%I #16 Nov 12 2020 03:32:19

%S 6,6,8,12,12,18,32,27,16,5,25,15,6,108,20,64,25,21,14,240,21,270,28,

%T 320,35,375,42,432,49,110,22,1680,33,1890,44,2240,55,2625,66,3024,77,

%U 3430,88,3840,99,4725,11,567,55,168,110,126,1320,378,2640,1134,3520,1701

%N a(n) = b(n+2)*b(n+1)/b(n), where b() = A160256().

%C By definition, each term of this sequence is a positive integer.

%H Alois P. Heinz, <a href="/A160257/b160257.txt">Table of n, a(n) for n = 1..10000</a>

%p bb:= proc(n) option remember; false end: b:= proc(n) option remember; local k, m; if n<3 then bb(n):= true; n else m:= denom(b(n-1) /b(n-2)); for k from m by m while bb(k) do od; bb(k):= true; k fi end: a:= n-> b(n+2) *b(n+1) /b(n): seq(a(n), n=1..100); # _Alois P. Heinz_, May 18 2009

%t bb[_] = False;

%t b[n_] := b[n] = Module[{k, m}, If[n<3, bb[n] = True; n, m = Denominator[ b[n-1]/b[n-2]]; For[k = m, bb[k], k += m]; bb[k] = True; k]];

%t a[n_] := b[n+2] b[n+1]/b[n];

%t Array[a, 100] (* _Jean-François Alcover_, Nov 12 2020, after _Alois P. Heinz_ *)

%Y Cf. A075076, A160256.

%K nonn,look

%O 1,1

%A _Leroy Quet_, May 06 2009

%E More terms from _Alois P. Heinz_, May 18 2009