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A079808 Consider a triangle in which the 2n-th row contains first 2n positive integers in decreasing order and the (2n+1)-st row contains first 2n+1 positive integers in increasing order; sequence contains concatenation of numbers read upward at a 45-degree angle. 4
1, 2, 11, 42, 133, 622, 1531, 8244, 17335, 102642, 193551, 1228446, 11137537, 142104662, 113395571, 1621248648, 11531157739, 182144106682, 117313597591, 20216412688410, 119315511779311, 2221841461086102, 1213175137995111 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
EXAMPLE
Triangle begins as:
1;
2 1;
1 2 3;
4 3 2 1;
1 2 3 4 5;
6 5 4 3 2 1;
MATHEMATICA
a[n_] := FromDigits[Join@@Table[IntegerDigits[If[EvenQ[n+1-i], n+2-2i, i]], {i, 1, Ceiling[n/2]}]]
CROSSREFS
Cf. A079809.
Sequence in context: A225907 A107020 A160945 * A089658 A219100 A140322
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Feb 10 2003
STATUS
approved

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Last modified April 23 15:20 EDT 2024. Contains 371916 sequences. (Running on oeis4.)