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A066686 Array T(i,j) read by antidiagonals, where T(i,j) is the concatenation of i and j (1<=i, 1<=j). 6

%I

%S 11,12,21,13,22,31,14,23,32,41,15,24,33,42,51,16,25,34,43,52,61,17,26,

%T 35,44,53,62,71,18,27,36,45,54,63,72,81,19,28,37,46,55,64,73,82,91,

%U 110,29,38,47,56,65,74,83,92,101,111,210,39,48,57,66,75,84,93,102,111

%N Array T(i,j) read by antidiagonals, where T(i,j) is the concatenation of i and j (1<=i, 1<=j).

%C The element at T(i,j) is the {(i+j-1)(i+j-2)/2 + i}-th element read in the sequence.

%H Alexander Bogomolny, <a href="http://www.cut-the-knot.org/do_you_know/numbers.shtml">What is a number?</a>

%H Boris Putievskiy, <a href="http://arxiv.org/abs/1212.2732">Transformations [Of] Integer Sequences And Pairing Functions</a>, arXiv preprint arXiv:1212.2732, 2012.

%e The array begins

%e 11 12 13 14 15 16 17 18 19 110 ...

%e 21 22 23 24 25 26 27 28 29 210 ...

%e 31 32 33 34 35 36 37 38 39 310 ...

%e 41 42 43 44 45 46 47 48 49 410 ...

%t a = {}; Do[ a = Append[a, ToExpression[ StringJoin[ ToString[k], ToString[n - k]]]], {n, 2, 13}, {k, 1, n - 1} ]; a

%K easy,nonn,tabl,base

%O 1,1

%A _Robert G. Wilson v_, Jan 11 2002

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Last modified September 24 05:29 EDT 2021. Contains 347623 sequences. (Running on oeis4.)