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A078942 Flipping burnt pancakes. Given a sorted stack of n burnt pancakes of different sizes (smallest on top, ..., largest at the bottom), each with its burnt side up, a(n) is the number of spatula flips needed to restore them to their initial order but with the burnt sides down. 2
1, 4, 6, 8, 10, 12, 14, 15, 17, 18, 19, 21, 22, 23, 24, 26, 28, 29 (list; graph; refs; listen; history; text; internal format)



In a 'spatula flip', a spatula is inserted below any pancake and all pancakes above the spatula are lifted and replaced in reverse order.

It is conjectured that this initial configuration is a worst case for the general problem of sorting burnt pancakes. If so, then this sequence is identical to A078941.


David S. Cohen and Manuel Blum, "On the problem of sorting burnt pancakes", Discrete Applied Math., 61 (1995) 105-120.


Table of n, a(n) for n=1..18.

Douglas B. West, The Pancake Problems (1975, 1979, 1973) - From N. J. A. Sloane, Jul 26 2012


a(n) <= A078941(n). a(n+1) <= a(n) + 2. 3n/2 <= a(n) <= 47n/30 + c for some constant c.


Cf. A078941, A058986.

Sequence in context: A090334 A272601 A078941 * A248419 A186389 A039767

Adjacent sequences:  A078939 A078940 A078941 * A078943 A078944 A078945




Dean Hickerson, Dec 18 2002



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Last modified May 26 23:31 EDT 2017. Contains 287189 sequences.