A336490 Consider the figure made up of a row of n adjacent congruent rectangles, with diagonals of all possible rectangles drawn; a(n) is the number of interior vertices where exactly four lines cross.

0, 0, 1, 2, 2, 10, 22, 18, 32, 62, 100, 118, 136, 154, 274, 346, 426, 554, 698, 726, 884, 1058, 1248, 1454, 1784, 2146, 2714, 2978, 3250, 3722, 4226, 4490, 5104, 5758, 6674, 7350, 8058, 8798, 10062, 11238, 12478, 14046, 15702, 16526, 18016, 19570, 21188, 22870

Offset

1,4

Links

Lars Blomberg, Table of n, a(n) for n = 1..500

Formula

It seems that a(n) = A018811(n+1) / 2 for n > 3. - Andrei Zabolotskii, Jun 06 2026

Crossrefs

Cf. A334701, A336489, A336491, A018811.

Column 8 of A333275.

Sequence in context: A358996 A192309 A151456 * A230893 A151389 A151428

Adjacent sequences: A336487 A336488 A336489 * A336491 A336492 A336493

Keyword

nonn,changed

Author

Lars Blomberg, Jul 25 2020

Status

approved