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.

1, 1, 32, 12, 521, 143, 7234, 1632, 92541, 18345, 1127436, 1103652, 13294561, 11238547, 1521147638, 1143105672, 17213496581, 11631258749, 19215411678310, 1183145107692, 212174136985101, 120316512789411, 232194156118710312

Offset: 1

Author

Amarnath Murthy, Feb 10 2003

Keywords

• base
• nonn

Examples

			Triangle begins with:
  1;
  1 2;
  3 2 1;
  1 2 3 4;
  5 4 3 2 1;
  1 2 3 4 5 6;
		

Links

• G. C. Greubel, Table of n, a(n) for n = 1..715

Crossrefs

Cf. A079808, A079810.

Programs

Mathematica

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