A056604 a(0)=1; thereafter a(n) = lcm(1, 2, 3, 4, ..., prime(n)).

1, 2, 6, 60, 420, 27720, 360360, 12252240, 232792560, 5354228880, 2329089562800, 72201776446800, 5342931457063200, 219060189739591200, 9419588158802421600, 442720643463713815200, 164249358725037825439200, 9690712164777231700912800, 591133442051411133755680800

Offset

0,2

Comments

Previous name was: Values of lcm[1,...,m], m = prime, whose squarefree kernels give A002110.

a(n) can be used like A006939(n) for certain kinds of rounding. E.g., the Babylonian a(3) = 60 = 2*2*3*5 divides A006939(3) = 360 = 2*2*2*3*3*5. - Frank Ellermann, Dec 18 2001

a(342) has 1000 decimal digits. - Michael De Vlieger, Mar 05 2017

Links

Michael De Vlieger, Table of n, a(n) for n = 0..342

Formula

a(n) = prime(n)^r(n) *...* prime(1)^r(1) for maximal prime(j)^r(j) <= prime(n).

a(n) = Product_{k=1..n} prime(k)^floor(log(prime(n))/log(prime(k))). - Daniel Suteu, Oct 09 2017

a(n) = A003418(prime(n)). - M. F. Hasler, Jan 04 2020

Example

a(5) = lcm(1,2,...,10,11) = 27720, prime(5) = 11. Not all possible lcm(1,..,n) values of A003418 occur, e.g., 12, 840, 25520, etc. are not present. Their squarefree kernels gives exactly A002110.

Maple

a:= n-> ilcm(`if`(n=0, NULL, $1..ithprime(n))):
seq(a(n), n=0..20);  # Alois P. Heinz, Dec 05 2014

Mathematica

Table[If[n == 0, 1, LCM @@ Range@ Prime@ n], {n, 0, 18}] (* Michael De Vlieger, Mar 05 2017 *)

Prog

(PARI) a(n)=lcm(vector(prime(n), i, i)) \\ Charles R Greathouse IV, Oct 27 2013
(PARI) apply( A056604(n)=lcm([2..if(n, prime(n))]), [0..20]) \\ Or A056604(n) = A003418(prime(n)), might be more efficient. - M. F. Hasler, Jan 04 2020
(Magma) [1] cat [Lcm([2..p]): p in PrimesUpTo(65)]; // Bruno Berselli, Feb 08 2015

Crossrefs

Cf. A002110, A003418, A006939, A034386, A051451.

Sequence in context: A334224 A226959 A083135 * A362702 A356259 A215720

Adjacent sequences: A056601 A056602 A056603 * A056605 A056606 A056607

Keyword

nonn

Author

Labos Elemer, Aug 07 2000

Extensions

a(16) from Frank Ellermann, Dec 18 2001

New name from Charles R Greathouse IV, Oct 27 2013

More terms from Alois P. Heinz, Dec 05 2014

a(0)=1 added to definition by N. J. A. Sloane, Jan 05 2020

Status

approved