Generating comma separated input for LCM

Question

I would like to calculate the Least Common Multiple of the 100 first numbers. I've tried with

LCM[Table[i, {i, 10}]]

But it produces a list instead of the right answer, a single number.

{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}

It seems that LCM doesn't like to get a list as the input.

What's the proper way to do it?

LCM takes a Sequence of numbers (not a List of numbers as input. Use LCM @@ Table[i, {i, 100}]? or LCM[Sequence @@ Table[i, {i, 100}]]. — kglr, Mar 19 '15 at 01:51
just posted the comment as an answer along with few additional ways to use a list as input to LCM. — kglr, Mar 19 '15 at 11:41
Related LCM & GCD demonstration http://demonstrations.wolfram.com/UnderstandingTheLeastCommonMultipleAndGreatestCommonDivisor/ — Gustavo Delfino, Mar 19 '15 at 12:15

score 1 · Accepted Answer · answered Mar 19 '15 at 11:39

1

LCM takes a Sequence of numbers (not a List of numbers) as input.

input = Table[i, {i, 100}];

You can use input in LCM in a number of ways:

LCM @@ input (* replace the `Head` of `input` by `LCM` *)
LCM[Sequence@@input] (* replace the `Head` of `input` by `Sequence` *)
input /. List -> LCM
input2 = input; ReplacePart[input2, 0 -> LCM]
input3 = input; input3[[0]]=LCM; input3
input4 = input; MapAt[LCM &, input4, {0}]

all give

69720375229712477164533808935312303556800

answered Mar 19 '15 at 11:39

kglr

394,356
18
477
896

What's the most efficient? – skan Mar 19 '15 at 11:48
@skan, not sure ... as far as i can tell, it seems they are more or less the same speedwise. – kglr Mar 19 '15 at 12:03
and memorywise? – skan Mar 19 '15 at 13:30
1

@skan, good question; i am afraid i don't know. By the way, you don't need to make copies of input to make use of the last 3 methods, you can make the replacements in-place. – kglr Mar 19 '15 at 13:50

Generating comma separated input for LCM

1 Answers1