1,2

p divides a(p-1) for prime p>3.

a(n) = ((2n)^(2n)-1)/(2n+1)/(2n-1). a(n) = A048861(2n)/(2n+1)/(2n-1). a(n) = A023037(2n)/(2n+1). a(n) = A089815(2n-2).

Table[((2n)^(2n)-1)/(2n+1)/(2n-1), {n, 1, 20}]

Cf. A048861 = n^n-1. Cf. A023037, A089815.

Adjacent sequences: A128539 A128540 A128541 this_sequence A128543 A128544 A128545

Sequence in context: A075602 A022012 A022546 this_sequence A067409 A007410 A072160

nonn

Alexander Adamchuk (alex(AT)kolmogorov.com), May 08 2007