A079809 - OEIS

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 #11 Dec 14 2023 15:40:08

%S 1,1,32,12,521,143,7234,1632,92541,18345,1127436,1103652,13294561,

%T 11238547,1521147638,1143105672,17213496581,11631258749,

%U 19215411678310,1183145107692,212174136985101,120316512789411,232194156118710312

%N 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 G. C. Greubel, <a href="/A079809/b079809.txt">Table of n, a(n) for n = 1..715</a>

%e Triangle begins with:

%e 1;

%e 1 2;

%e 3 2 1;

%e 1 2 3 4;

%e 5 4 3 2 1;

%e 1 2 3 4 5 6;

%t a[n_] := FromDigits[Join@@Table[IntegerDigits[If[OddQ[n+1-i], n+2-2i, i]], {i, 1, Ceiling[n/2]}]]

%Y Cf. A079808, A079810.

%K base,nonn

%O 1,3

%A _Amarnath Murthy_, Feb 10 2003