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 A107711 Triangle read by rows: T(0,0)=1, T(n,m) = binomial(n,m) * gcd(n,m)/n. 9
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 5, 10, 5, 1, 1, 1, 1, 3, 5, 5, 3, 1, 1, 1, 1, 7, 7, 35, 7, 7, 1, 1, 1, 1, 4, 28, 14, 14, 28, 4, 1, 1, 1, 1, 9, 12, 42, 126, 42, 12, 9, 1, 1, 1, 1, 5, 15, 30, 42, 42, 30, 15, 5, 1, 1, 1, 1, 11, 55, 165, 66, 462, 66, 165, 55, 11, 1, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,13 COMMENTS T(0,0) is an indeterminate, but 1 seems a logical value to assign it. T(n,0) = T(n,1) = T(n,n-1) = T(n,n) = 1. T(2n,n) = A001700(n-1) (n>=1). - Emeric Deutsch, Jun 13 2005 LINKS Reinhard Zumkeller, Rows n = 1..125 of triangle, flattened Wolfdieter Lang, On Collatz' Words, Sequences and Trees, arXiv:1404.2710 [math.NT], 2014 and J. Int. Seq. 17 (2014) # 14.11.7. FORMULA From Wolfdieter Lang, Feb 28 2014 (Start) T(n, m) = T(n-1,m)*(n-1)*gcd(n,m)/((n-m)*gcd(n-1,m)), n > m >= 1, T(n, 0) = 1, T(n, n) = 1, otherwise 0. T(n, m) = binomial(n-1,m-1)*gcd(n,m)/m for n >= m >= 1, T(n,0) = 1, otherwise 0 (from iteration of the preceding recurrence). T(n, m) = T(n-1, m-1)*(n-1)*gcd(n,m)/(m*gcd(n-1,m-1)) for n >= m >= 2, T(n, 0) = 1, T(n, 1) = 0, otherwise 0 (from the preceding formula). T(2*n, n) = A001700(n-1) (n>=1) (see the Emeric Deutsch comment above), T(2*n, n-1) = A234040(n), T(2*n+1,n) = A000108(n), n >= 0 (Catalan numbers). Column sequences: T(n+2, 2) = A026741(n+1), T(n+3, 3) = A234041(n), T(n+4, 4) = A208950(n+2), T(n+5, 5) = A234042, n >= 0. (End) EXAMPLE T(6,2)=5 because binomial(6,2)*gcd(6,2)/6 = 15*2/6 = 5. The triangle T(n,m) begins: n\m 0  1  2   3   4    5   6   7  8  9  10... 0:  1 1:  1  1 2:  1  1  1 3:  1  1  1   1 4:  1  1  3   1   1 5:  1  1  2   2   1    1 6:  1  1  5  10   5    1   1 7:  1  1  3   5   5    3   1   1 8:  1  1  7   7  35    7   7   1  1 9:  1  1  4  28  14   14  28   4  1  1 10: 1  1  9  12  42  126  42  12  9  1   1 n\m 0  1  2   3   4    5   6   7  8  9  10... ... reformatted - Wolfdieter Lang, Feb 23 2014 MAPLE a:=proc(n, k) if n=0 and k=0 then 1 elif k<=n then binomial(n, k)*gcd(n, k)/n else 0 fi end: for n from 0 to 13 do seq(a(n, k), k=0..n) od; # yields sequence in triangular form. - Emeric Deutsch, Jun 13 2005 MATHEMATICA T[0, 0] = 1; T[n_, m_] := Binomial[n, m] * GCD[n, m]/n; Table[T[n, m], {n, 1, 13}, {m, 1, n}] // Flatten (* Jean-François Alcover, Nov 16 2017 *) PROG (Haskell) a107711 n k = a107711_tabl !! n !! k a107711_row n = a107711_tabl !! n a107711_tabl = [1] : zipWith (map . flip div) [1..]                (tail \$ zipWith (zipWith (*)) a007318_tabl a109004_tabl) -- Reinhard Zumkeller, Feb 28 2014 CROSSREFS Cf. A007318, A001700, A000108, A234040, A026741, A234042. Cf. A109004. Sequence in context: A109673 A023591 A165661 * A242345 A179067 A061893 Adjacent sequences:  A107708 A107709 A107710 * A107712 A107713 A107714 KEYWORD tabl,nonn AUTHOR Leroy Quet, Jun 10 2005 EXTENSIONS More terms from Emeric Deutsch, Jun 13 2005 STATUS approved

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Last modified May 11 00:21 EDT 2021. Contains 343784 sequences. (Running on oeis4.)