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A280919 Precipices from the successive terraces, descending by the main diagonal of the pyramid described in A245092. Also first differences of A071562.

%I A280919 #50 Dec 31 2020 11:11:15
%S A280919 1,2,2,2,1,3,3,1,2,2,4,1,3,2,2,3,1,4,2,3,3,1,1,4,2,4,3,1,2,4,2,5,3,1,
%T A280919 3,4,2,1,5,2,1,1,4,4,2,2,5,3,1,5,2,2,2,3,5,3,1,6,3,1,2,4,2,3,3,1,1,6,
%U A280919 4,2,5,3,2,3,1,2,2,4,4,1,1,6,4,1,3,1,3
%N A280919 Precipices from the successive terraces, descending by the main diagonal of the pyramid described in A245092. Also first differences of A071562.
%C A280919 Descending by the main diagonal of the pyramid, A071562 gives the levels where we can find a terrace.
%C A280919 The terraces at the k-th level of the pyramid are also the parts of the symmetric representation of sigma(k).
%C A280919 a(n) is the length of the n-th vertical line segment at the main diagonal of the pyramid.
%C A280919 a(n) is the precipice of A071562(n).
%C A280919 The structure of the stepped pyramid arises after the 90-degree-zig-zag folding of the diagram of the isosceles triangle A237593.
%C A280919 The stepped pyramid is also one of the 3D-quadrants of the stepped pyramid described in A244050.
%C A280919 Equals nonzero terms of A259179. - _Omar E. Pol_, Apr 17 2018
%H A280919 Robert Price, <a href="/A280919/b280919.txt">Table of n, a(n) for n = 1..13750</a>
%H A280919 Omar E. Pol, <a href="http://www.polprimos.com/imagenespub/polpyr02.jpg">Illustration of the isosceles triangle of A237593 (rows 1..28)</a>
%H A280919 Omar E. Pol, <a href="http://www.polprimos.com/imagenespub/polpyr05.jpg">Perspective view of the pyramid (first 16 levels)</a>
%F A280919 a(n) = A280223(A071562(n)).
%t A280919 Differences@ Select[Range@ 228, Function[n, Total@ Select[Divisors@ n, Sqrt[n/2] <= # < Sqrt[2 n] &] != 0]] (* _Michael De Vlieger_, Jan 13 2017, after _Robert G. Wilson v_ at A071562 *)
%Y A280919 For more information about the precipices see A276112, A277437, A280223 and A280295.
%Y A280919 Cf. A000203, A071562, A196020, A235791, A236104, A237048, A237591, A237593, A237270, A237271, A244050, A245092, A259179, A262626.
%K A280919 nonn
%O A280919 1,2
%A A280919 _Omar E. Pol_, Jan 10 2017
%E A280919 More terms from _Michael De Vlieger_, Jan 13 2017