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

3,2

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

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}]

Crossrefs

Sequence in context: A085216 A300663 A102310 * A117936 A264766 A251090

Adjacent sequences: A151543 A151544 A151545 * A151547 A151548 A151549

Keyword

nonn,look

Author

N. J. A. Sloane, May 16 2009

Status

approved