A052442 Number of simple unlabeled n-node graphs of connectivity 1.

0, 1, 1, 3, 11, 56, 385, 3994, 67014, 1973029, 105731474, 10439496931, 1902968718515, 641662974453892, 401490336727861176, 467924684115578671326, 1019752390010650509117288, 4171131179469162937375841939, 32134378048921787829834095722663, 467778894124037894839737804918978194

Offset

1,4

Links

Jean-François Alcover, Table of n, a(n) for n = 1..26

Jens M. Schmidt, Data files in graph6 format

Eric Weisstein's World of Mathematics, k-Connected Graph.

Eric Weisstein's World of Mathematics, Biconnected Graph

Formula

a(n) = A001349(n) - A002218(n) for n > 2. - Andrew Howroyd, Sep 04 2019

Mathematica

A001349 = Cases[Import["https://oeis.org/A001349/b001349.txt", "Table"], {_, _}][[All, 2]];
A002218 = Cases[Import["https://oeis.org/A002218/b002218.txt", "Table"], {_, _}][[All, 2]];
a[1] = 0; a[2] = 1;
a[n_] := A001349[[n+1]] - A002218[[n]];
Array[a, 26] (* Jean-François Alcover, Sep 10 2019, after Andrew Howroyd *)

Crossrefs

Column k=1 of A259862.

Cf. A000719, A052443, A052444, A052445.

Sequence in context: A000985 A207433 A094611 * A217034 A330351 A180112

Adjacent sequences: A052439 A052440 A052441 * A052443 A052444 A052445

Keyword

nonn

Author

Eric W. Weisstein

Extensions

Terms a(8)-a(11) by Jens M. Schmidt, Feb 18 2019

a(1)-a(2) corrected by Andrew Howroyd, Aug 28 2019

a(12)-a(20) from Andrew Howroyd, Sep 04 2019

Status

approved