A055974 Number of unlabeled digraphs with loops (relations) on n nodes and with an odd number of arcs.

0, 1, 4, 52, 1504, 145984, 48461696, 56141454464, 229148544420864, 3333310786076963968, 174695272746603272722432, 33301710992539090379269318144, 23278728241293494481773139193036800, 60084295633556503802059558812644803074048, 576025077880237078776946485247979728479746359296

Offset: 0

Author

Vladeta Jovovic, Jul 19 2000

Keywords

• easy
• nonn

Links

• Andrew Howroyd, Table of n, a(n) for n = 0..50

Crossrefs

Cf. A000171, A000595, A047832, A054960, A055973.

Formula

a(2*n) = (A000595(2*n) - A047832(n))/2; a(2*n+1) = A000595(2*n+1)/2.

a(n) = (A000595(n) - A000171(2*n+1))/2.

Extensions

a(0)=0 prepended and terms a(13) and beyond from Andrew Howroyd, Apr 19 2020