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A280295 Smallest number with precipice n. Descending by the main diagonal of the pyramid described in A245092, the height difference between the level a(n) (starting from the top) and the level of the next terrace is equal to n. 7
1, 2, 9, 20, 72, 144 (list; graph; refs; listen; history; text; internal format)



The structure of the step pyramid arises after the 90-degree-zig-zag folding of the diagram of the isosceles triangle A237593.

The terraces at the k-th level of the pyramid are also the parts of the symmetric representation of sigma(k), k >= 1.

The step pyramid is also one of the 3D-quadrants of the step pyramid described in A244050.

For more information about the precipices see A277437 and A280223.

Is this sequence infinite?


Table of n, a(n) for n=1..6.

Omar E. Pol, Perspective view of the pyramid (first 16 steps)


a(3) = 9 because descending by the main diagonal of the pyramid, the height difference between the level 9 and the level of the next terrace is equal to 3, and 9 is the smallest number with this property.


Row 1 of A277437.

Cf. A000203, A196020, A235791, A236104, A237591, A237593, A240542, A244050, A245092, A259179, A262626, A276112, A277437, A279286, A279385, A280223.

Sequence in context: A259035 A093835 A264294 * A041007 A002360 A100516

Adjacent sequences:  A280292 A280293 A280294 * A280296 A280297 A280298




Omar E. Pol, Dec 31 2016


a(6) from Omar E. Pol, Jan 02 2017



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Last modified November 15 21:29 EST 2019. Contains 329151 sequences. (Running on oeis4.)