A127231 -id:A127231 - cp's OEIS frontend

A127230 a(n) = (2n)! - 1.

1, 23, 719, 40319, 3628799, 479001599, 87178291199, 20922789887999, 6402373705727999, 2432902008176639999, 1124000727777607679999, 620448401733239439359999, 403291461126605635583999999, 304888344611713860501503999999, 265252859812191058636308479999999

Offset: 1

Artur Jasinski, Jan 09 2007

nonn

Cf. A010050, A028387, A062938, A127227, A127228, A127229, A127231.

Mathematica
```
Table[(2n)! - 1, {n, 1, 30}]
```

a(n) = -1 + A010050(n).

Entry revised by Alois P. Heinz, Mar 27 2021

A067241 Numbers k such that gcd((2*k)!+1, k!+1) > 1.

Original entry on oeis.org

3, 5, 8, 9, 21, 23, 33, 39, 51, 63, 65, 81, 89, 95, 99, 113, 131, 173, 183, 191, 209, 215, 221, 239, 245, 251, 261, 281, 285, 299, 303, 309, 315, 341, 345, 363, 369, 371, 393, 411, 419, 431, 443, 473, 495, 509, 525, 543, 545, 561, 575, 593, 645, 659, 683, 711

Offset: 1

Benoit Cloitre, Feb 20 2002

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A038507, A127231.

q[k_] := !CoprimeQ[(2*k)!+1, k!+1]; Select[Range[720], q] (* Amiram Eldar, May 01 2025 *)

isok(k) = gcd((2*k)!+1, k!+1) > 1; \\ Amiram Eldar, May 01 2025

cp's OEIS Frontend

A127230 a(n) = (2n)! - 1.

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