A066332 a(1)=1; for n > 0, a(n+1) = rad(a(n))*n where rad=A007947.

1, 1, 2, 6, 24, 30, 180, 210, 1680, 1890, 2100, 2310, 27720, 30030, 420420, 450450, 480480, 510510, 9189180, 9699690, 193993800, 203693490, 213393180, 223092870, 5354228880, 5577321750, 5800414620, 6023507490, 6246600360, 6469693230, 194090796900, 200560490130

Offset: 1

Author

Reinhard Zumkeller, Jan 05 2002

Keywords

• nonn

Crossrefs

Cf. A002110, A008864, A049614.

Programs

Mathematica

rad[n_] := Times @@ (First@# & /@ FactorInteger@n); a[n_] := (n -1)rad[a[n -1]]; a[1] = 1; Array[a, 30] (* Robert G. Wilson v, Dec 14 2016 and modified Dec 24 2016 *)

PARI

a(n) = if(n==1, 1, (n-1)*prod(k=1, primepi(n-2), prime(k))); \\ Daniel Suteu, Dec 14 2016

PARI

rad(n) = factorback(factorint(n)[, 1]);
a(n) = if (n==1, 1, (n-1)*rad(a(n-1))); \\ Michel Marcus, Dec 21 2016

Formula

a(1)=1; for n > 1, a(n) = (n-1) * Product_{p prime < (n-1)} p. - Pedro Caceres, Mar 12 2018

a(A008864(n)) = A002110(n). - Michel Marcus, Mar 17 2018

Extensions

More terms from Michel Marcus, Mar 17 2018