A342761 Fold a square sheet of paper alternately vertically to the left and horizontally downwards; after each fold, draw a line along each inward crease; after n folds, the resulting graph has a(n) edges.

4, 7, 10, 15, 25, 43, 79, 147, 283, 547, 1075, 2115, 4195, 8323, 16579, 33027, 65923, 131587, 262915, 525315, 1050115, 2099203, 4197379, 8392707, 16783363, 33562627, 67121155, 134234115, 268460035, 536903683, 1073790979

Offset: 0

Author

Rémy Sigrist and N. J. A. Sloane, Mar 22 2021

Keywords

• nonn

Comments

A342759 is the main sequence for this entry.

Examples

			See illustration in Links section.
		

Links

• Rémy Sigrist, Illustration of initial terms
• Rémy Sigrist, C# program for A342761

Crossrefs

Cf. A342759.

It appears that a(n) = A257418(n) + 2 for n >= 2. Hugo Pfoertner, Mar 29 2021 [This is true - N. J. A. Sloane, Apr 26 2021]

Formula

Theorem: a(2*t) = 2^(2*t)+3*2^(t-1)+3 for t >= 1; a(2*t+1) = 2^(2*t+1)+2^(t+1)+3 for t >= 0. - N. J. A. Sloane, Apr 26 2021