

A003987


Table of n XOR m (or Nimsum of n and m) read by antidiagonals, i.e. with entries in the order (n,m) = (0,0),(0,1),(1,0),(0,2),(1,1),(2,0),...


51



0, 1, 1, 2, 0, 2, 3, 3, 3, 3, 4, 2, 0, 2, 4, 5, 5, 1, 1, 5, 5, 6, 4, 6, 0, 6, 4, 6, 7, 7, 7, 7, 7, 7, 7, 7, 8, 6, 4, 6, 0, 6, 4, 6, 8, 9, 9, 5, 5, 1, 1, 5, 5, 9, 9, 10, 8, 10, 4, 2, 0, 2, 4, 10, 8, 10, 11, 11, 11, 11, 3, 3, 3, 3, 11, 11, 11, 11, 12, 10, 8, 10, 12, 2, 0, 2, 12, 10, 8, 10, 12, 13, 13, 9, 9
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OFFSET

0,4


COMMENTS

Another way to construct the array: construct an infinite square matrix starting in the top left corner using the rule that each entry is the smallest nonnegative number that is not in the row to your left or in the column above you.
After a few moves the matrix looks like this:
01234...
10325...
2301?
The ? is then replaced by 6.


REFERENCES

J.P. Allouche and J. Shallit, The ring of kregular sequences, II, Theoret. Computer Sci., 307 (2003), 329.
J. H. Conway, On Numbers and Games. Academic Press, NY, 1976, pp. 5153.
D. Gale, Tracking the Automatic Ant and Other Mathematical Explorations, A Collection of Mathematical Entertainments Columns from The Mathematical Intelligencer, Springer, 1998; see p. 190. [From N. J. A. Sloane, Jul 14 2009]
R. K. Guy, Impartial games, pp. 3555 of Combinatorial Games, ed. R. K. Guy, Proc. Sympos. Appl. Math., 43, Amer. Math. Soc., 1991.


LINKS

T. D. Noe, Rows n=0..100 of triangle, flattened
J.P. Allouche and J. Shallit, The Ring of kregular Sequences, II
N. J. A. Sloane, My favorite integer sequences, in Sequences and their Applications (Proceedings of SETA '98).
Index entries for sequences related to Nimsums


FORMULA

T[2i,2j] = 2T[i,j], T[2i+1,2j] = 2T[i,j] + 1.


EXAMPLE

Table begins
0 1 2 3 4 5 6 7 ...
1 0 3 2 5 4 7 6 ...
2 3 0 1 6 7 4 5 ...
3 2 1 0 7 6 5 4 ...
4 5 6 7 0 1 2 3 ...
5 4 7 6 1 0 3 2 ...
6 7 4 5 2 3 0 1 ...
7 6 5 4 3 2 1 0 ...
...................


MAPLE

nimsum := proc(a, b) local t1, t2, t3, t4, l; t1 := convert(a+2^20, base, 2); t2 := convert(b+2^20, base, 2); t3 := evalm(t1+t2); map(x>x mod 2, t3); t4 := convert(evalm(%), list); l := convert(t4, base, 2, 10); sum(l[k]*10^(k1), k=1..nops(l)); end; # memo: adjust 2^20 to be much bigger than a and b
AT := array(0..N, 0..N); for a from 0 to N do for b from a to N do AT[a, b] := nimsum(a, b); AT[b, a] := AT[a, b]; od: od:
# alternative:
read("transforms") :
A003987 := proc(n, m)
XORnos(n, m) ;
end proc: # R. J. Mathar, Apr 17 2013


MATHEMATICA

Flatten[Table[BitXor[b, a  b], {a, 0, 10}, {b, 0, a}]] (* BitXor and Nim Sum are equivalent *)


CROSSREFS

Initial rows are A001477, A004442, A004443, A004444, etc. Cf. A051775, A051776.
Cf. A003986 (OR) and A004198 (AND).
Antidiagonal sums are in A006582.
Sequence in context: A002125 A171731 A185815 * A141692 A245230 A063180
Adjacent sequences: A003984 A003985 A003986 * A003988 A003989 A003990


KEYWORD

tabl,nonn,nice,look


AUTHOR

Marc LeBrun


EXTENSIONS

Corrected and formatted example, Tilman Piesk, May 29 2011.


STATUS

approved



