cp's OEIS Frontend

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.

%I A342761 #12 Apr 26 2021 14:22:14
%S A342761 4,7,10,15,25,43,79,147,283,547,1075,2115,4195,8323,16579,33027,65923,
%T A342761 131587,262915,525315,1050115,2099203,4197379,8392707,16783363,
%U A342761 33562627,67121155,134234115,268460035,536903683,1073790979
%N 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.
%C A342761 A342759 is the main sequence for this entry.
%H A342761 Rémy Sigrist, <a href="/A342761/a342761.png">Illustration of initial terms</a>
%H A342761 Rémy Sigrist, <a href="/A342761/a342761.txt">C# program for A342761</a>
%F A342761 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
%e A342761 See illustration in Links section.
%o A342761 (C#) See Links section.
%Y A342761 Cf. A342759.
%Y A342761 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]
%K A342761 nonn
%O A342761 0,1
%A A342761 _Rémy Sigrist_ and _N. J. A. Sloane_, Mar 22 2021