cp's OEIS Frontend

A108039 Replace each entry 2^i(2j+1) of the triangle in A008280 with i and replace 0's with *'s; then the entries n in the new triangle do not occur beyond diagonal a(n), measured from the left edge and taking the left edge to be diagonal number 1.

%I A108039 #15 Nov 06 2018 13:17:41
%S A108039 2,4,4,4,8,8,8,8,10,12,12,16,16,16,16,16,18,20
%N A108039 Replace each entry 2^i(2j+1) of the triangle in A008280 with i and replace 0's with *'s; then the entries n in the new triangle do not occur beyond diagonal a(n), measured from the left edge and taking the left edge to be diagonal number 1.
%H A108039 V. I. Arnold, <a href="http://dx.doi.org/10.1215/S0012-7094-91-06323-4">Bernoulli-Euler updown numbers associated with function singularities, their combinatorics and arithmetics</a>, Duke Math. J. 63 (1991), 537-555.
%H A108039 Sanjay Ramassamy, <a href="https://arxiv.org/abs/1712.08666">Modular periodicity of the Euler numbers and a sequence by Arnold</a>, arXiv:1712.08666 [math.CO], 2017.
%e A108039 3's do not occur beyond the 4th diagonal, so a(3) = 4.
%e A108039 Triangle begins:
%e A108039        *
%e A108039       * 0
%e A108039      0 0 *
%e A108039     * 0 1 1
%e A108039    0 0 2 1 *
%e A108039   * 0 1 1 4 4
%Y A108039 Cf. A008280.
%K A108039 nonn,more
%O A108039 0,1
%A A108039 _N. J. A. Sloane_, Jun 01 2005
%E A108039 Corrected and extended by _Sanjay Ramassamy_, Nov 03 2018