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A079809 Consider a triangle in which the 2n-th row contains first 2n positive integers in increasing order and the (2n+1)-st row contains first 2n+1 positive integers in decreasing order; sequence contains concatenation of numbers read upward at a 45-degree angle.

%I A079809 #11 Dec 14 2023 15:40:08
%S A079809 1,1,32,12,521,143,7234,1632,92541,18345,1127436,1103652,13294561,
%T A079809 11238547,1521147638,1143105672,17213496581,11631258749,
%U A079809 19215411678310,1183145107692,212174136985101,120316512789411,232194156118710312
%N A079809 Consider a triangle in which the 2n-th row contains first 2n positive integers in increasing order and the (2n+1)-st row contains first 2n+1 positive integers in decreasing order; sequence contains concatenation of numbers read upward at a 45-degree angle.
%H A079809 G. C. Greubel, <a href="/A079809/b079809.txt">Table of n, a(n) for n = 1..715</a>
%e A079809 Triangle begins with:
%e A079809   1;
%e A079809   1 2;
%e A079809   3 2 1;
%e A079809   1 2 3 4;
%e A079809   5 4 3 2 1;
%e A079809   1 2 3 4 5 6;
%t A079809 a[n_] := FromDigits[Join@@Table[IntegerDigits[If[OddQ[n+1-i], n+2-2i, i]], {i, 1, Ceiling[n/2]}]]
%Y A079809 Cf. A079808, A079810.
%K A079809 base,nonn
%O A079809 1,3
%A A079809 _Amarnath Murthy_, Feb 10 2003