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A343558
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Irregular triangle read by rows: the n-th row gives the row indices of the consecutive elements of the spiral of the n X n matrix defined in A126224.
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2
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1, 1, 1, 2, 2, 1, 1, 1, 2, 3, 3, 3, 2, 2, 1, 1, 1, 1, 2, 3, 4, 4, 4, 4, 3, 2, 2, 2, 3, 3, 1, 1, 1, 1, 1, 2, 3, 4, 5, 5, 5, 5, 5, 4, 3, 2, 2, 2, 2, 3, 4, 4, 4, 3, 3, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6, 6, 6, 6, 6, 5, 4, 3, 2, 2, 2, 2, 2, 3, 4, 5, 5, 5, 5, 4, 3, 3, 3, 4, 4
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OFFSET
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1,4
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LINKS
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EXAMPLE
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The triangle begins
1
1 1 2 2
1 1 1 2 3 3 3 2 2
1 1 1 1 2 3 4 4 4 4 3 2 2 2 3 3
...
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MATHEMATICA
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a:={}; nmax:=6; For[n=1, n<=nmax, n++, For[s=1, s<=2n-1, s++, If[OddQ[s] &&Mod[s, 4]==1, k=Ceiling[s/4]; For[i=1, i<=Ceiling[n-s/2], i++, AppendTo[a, k]], If[EvenQ[s]&&Mod[s, 4]==2, For[i=1, i<=Ceiling[n-s/2], i++, AppendTo[a, k+i]]; k+=Ceiling[n-s/2], If[EvenQ[s]&&Mod[s, 4]==0, For[i=1, i<=Ceiling[n-s/2], i++, AppendTo[a, k-i]]; k=k-i+1, For[i=1, i<=Ceiling[n-s/2], i++, AppendTo[a, k]]]]]]]; a
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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