A151546 When computing A160256(n), it must be a multiple of a(n).

1, 2, 3, 2, 3, 8, 9, 8, 3, 2, 6, 1, 6, 5, 12, 5, 12, 1, 60, 7, 60, 7, 60, 7, 60, 7, 60, 7, 60, 1, 420, 11, 420, 11, 420, 11, 420, 11, 420, 11, 420, 11, 420, 11, 420, 22, 378, 55, 126, 55, 63, 220, 63, 440, 189, 880, 567, 880, 189, 220, 63, 55, 252, 275, 252, 275, 336, 275, 84, 275, 84

Offset: 3

Author

N. J. A. Sloane, May 16 2009

Keywords

• nonn
• look

Comments

In other words, a(n) = numerator of b(n-2)/b(n-1), where b() = A160256().

Then b(n) = smallest multiple of a(n) not already present in A160256.

Links

• Alois P. Heinz, Table of n, a(n) for n = 3..10000

Programs

Maple

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-> numer(b(n-2) /b(n-1)): seq(a(n), n=3..100); # Alois P. Heinz, May 17 2009

Mathematica

bb[n_] := bb[n] = False;
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 ]];
a[n_] := Numerator[b[n - 2] /b[n - 1]];
Table[a[n], {n, 3, 100}]