A375921 a(n) = LCM(1,2, ..., 2n+1)/6.

1, 10, 70, 420, 4620, 60060, 60060, 2042040, 38798760, 38798760, 892371480, 4461857400, 13385572200, 388181593800, 12033629407800, 24067258815600, 24067258815600, 890488576177200, 890488576177200, 36510031623265200, 1569931359800403600, 1569931359800403600

Offset: 1

Author

Gregory Gerard Wojnar, Sep 02 2024

Keywords

• nonn

Comments

Agrees largely with A101029. The first difference is at n=8 for which a(8)/A101029(8) = 5. There are also other differences; the ratio of the two series entries appears to be always an integer.

Links

• Gregory Gerard Wojnar, Table of n, a(n) for n = 1..50

Crossrefs

Cf. A003418, A101029.

Programs

Mathematica

a[n_]:= LCM@@Range[1,2n+1]/6; Array[a,22] (* Stefano Spezia, Sep 02 2024 *)

PARI

a(n) = lcm([1..2*n+1])/6; \\ Michel Marcus, Sep 02 2024

Python

from math import lcm
def A375921(n): return lcm(*range(1,n+1<<1))//6 # Chai Wah Wu, Sep 26 2024

Formula

a(n) = A003418(2n+1)/6.