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A257608
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Triangle read by rows: T(n,k) = t(n-k, k); t(n,m) = f(m)*t(n-1,m) + f(n)*t(n,m-1), where f(x) = 9*x + 1.
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5
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1, 1, 1, 1, 20, 1, 1, 219, 219, 1, 1, 2218, 8322, 2218, 1, 1, 22217, 220222, 220222, 22217, 1, 1, 222216, 5006247, 12332432, 5006247, 222216, 1, 1, 2222215, 105340629, 530539235, 530539235, 105340629, 2222215, 1, 1, 22222214, 2123693776, 19700767514, 39259903390, 19700767514, 2123693776, 22222214, 1
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,5
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LINKS
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FORMULA
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T(n, k) = t(n-k, k), where t(n,k) = f(k)*t(n-1, k) + f(n)*t(n, k-1), and f(n) = 9*n + 1.
T(n, k) = (a*k + b)*T(n-1, k) + (a*(n-k) + b)*T(n-1, k-1), with T(n, 0) = T(n, n) = 1, a = 9, and b = 1. - G. C. Greubel, Mar 20 2022
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EXAMPLE
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Triangle begins as:
1;
1, 1;
1, 20, 1;
1, 219, 219, 1;
1, 2218, 8322, 2218, 1;
1, 22217, 220222, 220222, 22217, 1;
1, 222216, 5006247, 12332432, 5006247, 222216, 1;
1, 2222215, 105340629, 530539235, 530539235, 105340629, 2222215, 1;
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MATHEMATICA
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T[n_, k_, a_, b_]:= T[n, k, a, b]= If[k<0 || k>n, 0, If[k==0 || k==n, 1, (a*(n-k)+b)*T[n-1, k-1, a, b] + (a*k+b)*T[n-1, k, a, b]]];
Table[T[n, k, 9, 1], {n, 0, 12}, {k, 0, n}]//Flatten (* G. C. Greubel, Mar 20 2022 *)
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PROG
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(Sage)
if (k<0 or k>n): return 0
elif (k==0 or k==n): return 1
else: return (a*k+b)*T(n-1, k, a, b) + (a*(n-k)+b)*T(n-1, k-1, a, b)
flatten([[T(n, k, 9, 1) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, Mar 20 2022
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CROSSREFS
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Similar sequences listed in A256890.
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KEYWORD
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AUTHOR
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STATUS
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approved
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