A392425 Number of vertices in a complete bipartite graph where the vertices in the two parts are placed on opposite sides of a parabola at integer x coordinates |x| = 1, 2, ...n.

2, 5, 15, 42, 100, 205, 393, 676, 1101, 1710, 2518, 3637, 5049, 6860, 9074, 11783, 15097, 19039, 23825, 29473, 35966, 43545, 52183, 62338, 73662, 86429, 100969, 116904, 134700, 154855, 177367, 202225, 229190, 259043, 291512, 326737, 365445, 407764, 453394

Offset

1,1

Links

Table of n, a(n) for n=1..39.

Scott R. Shannon, Illustration for n = 2.

Scott R. Shannon, Illustration for n = 3.

Scott R. Shannon, Illustration for n = 4.

Scott R. Shannon, Illustration for n = 5.

Scott R. Shannon, Illustration for n = 6.

Scott R. Shannon, Illustration for n = 10.

Formula

a(n) = A392427(n) - A392426(n) + 1 by Euler's formula.

Crossrefs

Cf. A392426 (regions), A392427 (edges), A392442 (integer y), A331755.

Sequence in context: A190140 A006649 A379629 * A392442 A303980 A148350

Adjacent sequences: A392422 A392423 A392424 * A392426 A392427 A392428

Keyword

nonn

Author

Scott R. Shannon, Jan 11 2026

Status

approved