A066616 a(1) = 1; a(n) = n*a(n-1) if n does not divide a(n-1), otherwise a(n) = a(n-1).

1, 2, 6, 24, 120, 120, 840, 840, 7560, 7560, 83160, 83160, 1081080, 1081080, 1081080, 17297280, 294053760, 294053760, 5587021440, 5587021440, 5587021440, 5587021440, 128501493120, 128501493120, 3212537328000, 3212537328000

Offset

1,2

Links

Harry J. Smith, Table of n, a(n) for n = 1..200

Formula

a(1) = 1; for n > 1, a(n) = A059896(a(n-1), n). - Peter Munn, Jul 12 2022

Example

a(5) = 120; as 6 divides a(5), we have a(6) = a(5) = 120. Though 9 is not coprime to a(8) but still 9 does not divide a(8) so a(9) = 9 * a(8).

Mathematica

nxt[{n_, a_}]:={n+1, If[Mod[a, n+1]==0, a, a(n+1)]}; NestList[nxt, {1, 1}, 30][[All, 2]] (* Harvey P. Dale, Jul 01 2022 *)

Prog

(PARI) { for (n=1, 200, if (n==1, a=1, if (a%n, a=n*a)); write("b066616.txt", n, " ", a) ) } \\ Harry J. Smith, Mar 12 2010

Crossrefs

Cf. A003418, A037992 (duplicates removed).

Replacing A059896 with A059897 in the formula gives A284567.

Sequence in context: A242427 A319545 A362698 * A340516 A340515 A308819

Adjacent sequences: A066613 A066614 A066615 * A066617 A066618 A066619

Keyword

nonn

Author

Amarnath Murthy, Dec 24 2001

Extensions

More terms from Vladeta Jovovic, Dec 26 2001

Status

approved