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

0,3

Links

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

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.

Crossrefs

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

Sequence in context: A280571 A343429 A277353 * A009671 A015001 A355612

Adjacent sequences: A055971 A055972 A055973 * A055975 A055976 A055977

Keyword

easy,nonn

Author

Vladeta Jovovic, Jul 19 2000

Extensions

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

Status

approved