A262022 Denominator of partial sums of a reordered alternating harmonic series.

1, 3, 6, 30, 210, 420, 1260, 13860, 13860, 180180, 180180, 360360, 6126120, 116396280, 23279256, 23279256, 535422888, 535422888, 13385572200, 40156716600, 40156716600, 1164544781400, 36100888223400, 72201776446800, 72201776446800

Offset

0,2

Comments

See A262031 for this reordered alternating harmonic series with partial sums s(n).

Links

Table of n, a(n) for n=0..24.

Formula

a(n) = denominator(s(n)) with s(n) = Sum_{k=0..n} c(k), where c(k) = 3/(4*k+3), 3/(4*k+5), -3/(2*(k+1)) if k == 0, 1, 2 (mod 3), respectively.

Example

See A262031 for s(n), n=0..11, and s(10^n) for n=0..6.

Prog

(PARI) lista(nn) = {my(s = 0); for (k=0, nn, if (k%3==2, t = -3/(2*(k+1)), if (k%3==1, t = 3/(4*k+5), t = 3/(4*k+3))); s += t; print1(denominator(s), ", "); ); } \\ Michel Marcus, Sep 13 2015

Crossrefs

Cf. A262031, A262023.

Sequence in context: A372024 A133799 A347925 * A088436 A088506 A061137

Adjacent sequences: A262019 A262020 A262021 * A262023 A262024 A262025

Keyword

nonn,frac,easy

Author

Wolfdieter Lang, Sep 08 2015

Status

approved