A390227 a(n) = A392686(n)/2.

1, 45, 1575, 315315, 6891885, 160044885, 21751554825, 2183521465125, 76714387474725, 3172365552631275, 143758249516606725, 6770328989139240525, 2421128518942184926875, 138585396424250665214325, 148850981344565529304275, 572660521987304535825815775, 46892797085809056283503525

Offset

0,2

Links

Table of n, a(n) for n=0..16.

Formula

a(n) = denominator((Pi + 2*LerchPhi(-1, 1, 3/2 + 2*n))/(2*(4*n + 2))).

Mathematica

a[n_]:=Denominator[Sum[(-1)^i/(2i+1), {i, 0, 2n}]/((2n+1))]; Array[a, 17, 0]

Crossrefs

Cf. A016825, A392686.

Sequence in context: A014940 A273436 A049397 * A215859 A143170 A328351

Adjacent sequences: A390224 A390225 A390226 * A390228 A390229 A390230

Keyword

nonn,frac

Author

Stefano Spezia, Jan 20 2026

Status

approved