A280305 a(n) = (n^(2n) - (n-1)^(2n))/(2n-1).

1, 5, 133, 8425, 968561, 175694701, 46142992981, 16549469742737, 7769425693383361, 4623280765312793221, 3400130923182845767301, 3028135414242749262553465, 3211431367839213404127361393, 3999028255132797763368898027805, 5777573340599982456777597457984981

Offset

1,2

Comments

n such that a(n) is divisible by a square > 1: 4, 15, 22, 27, ...

Links

Harvey P. Dale, Table of n, a(n) for n = 1..214

Example

a(2) = 5 because (2^(2*2) - (2-1)^(2*2))/(2*2-1) = 5.

Mathematica

Table[(n^(2n)-(n-1)^(2n))/(2n-1), {n, 20}] (* Harvey P. Dale, Nov 03 2025 *)

Prog

(Magma) [(n^(2*n) - (n-1)^(2*n))/(2*n-1): n in [1..15]];

Crossrefs

Cf. A280302.

Sequence in context: A296191 A114474 A344395 * A085506 A307084 A132508

Adjacent sequences: A280302 A280303 A280304 * A280306 A280307 A280308

Keyword

nonn

Author

Juri-Stepan Gerasimov, Jan 03 2017

Status

approved