A051844 a(n) = LCM_{k=0..n} (2^k + 1).

2, 6, 30, 90, 1530, 16830, 218790, 9407970, 2417848290, 137817352530, 28252557268650, 19296496614487950, 4650455684091595950, 12700394473254148539450, 41619192688853844763777650, 13775952780010622616810402150, 902834617343556174437903325704550

Offset: 0

Author

Jeffrey Shallit, Apr 20 2000

Keywords

• nonn

Examples

			a(3) = lcm(2, 3, 5) = 30.
		

Crossrefs

Cf. A034268.

Cf. A019320.

Programs

Mathematica

Module[{nn=20,c},c=Table[2^n+1,{n,0,nn}];Table[LCM@@Take[c,n],{n,nn}]] (* Harvey P. Dale, Aug 04 2017 *)

PARI

a(n) = {ret = 1; for (k=0, n, ret = lcm(ret, 2^k+1)); return(ret);} \\ Michel Marcus, May 24 2013

Python

from math import lcm
from itertools import accumulate
def aupton(nn): return list(accumulate((2**k+1 for k in range(nn+1)), lcm))
print(aupton(16)) # Michael S. Branicky, Jul 04 2022

Formula

a(n) = lcm(2, 3, 5, ..., 2^n + 1).

Product_{k=1..n} cyclotomic(2*k-2, 2). - Vladeta Jovovic, Apr 05 2004

Extensions

More terms from Harvey P. Dale, Aug 04 2017