A079809 - OEIS

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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.

4

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

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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