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A138045
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Triangle read by rows: largest proper divisor of n as a table, ones excluded.
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1
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0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,8
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COMMENTS
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LINKS
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FORMULA
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T(n,k) = if k==A032742(n) and n(T(n,k))==n(A032742(n)) and k>1 then k else 0 (1<=k<=n), T(1,1)=0.
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EXAMPLE
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The first few terms of the table are:
0
0,0
0,0,0
0,2,0,0
0,0,0,0,0
0,0,3,0,0,0
0,0,0,0,0,0,0
0,0,0,4,0,0,0,0
0,0,3,0,0,0,0,0,0
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PROG
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(PARI)
up_to = 23220; \\ binomial(215+1, 2)
A032742(n) = if(1==n, n, n/vecmin(factor(n)[, 1]));
A138045tr(n, k) = if((k>1) && (A032742(n)==k), k, 0);
A138045list(up_to) = { my(v = vector(up_to), i=0); for(n=1, oo, for(k=1, n, i++; if(i > up_to, return(v)); v[i] = A138045tr(n, k))); (v); };
v138045 = A138045list(up_to);
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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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