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

1,3

Links

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

Example

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

Mathematica

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

Crossrefs

Cf. A079808, A079810.

Sequence in context: A302893 A303628 A070616 * A070629 A304228 A305038

Adjacent sequences: A079806 A079807 A079808 * A079810 A079811 A079812

Keyword

base,nonn

Author

Amarnath Murthy, Feb 10 2003

Status

approved