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 A093423 Consider the triangle whose first part is shown as an example in the entry A093422. If the n-th term of the triangle read by rows is a fraction then a(n) is the denominator of the fraction, otherwise a(n)=1. 3
 1, 1, 3, 1, 5, 1, 1, 7, 3, 5, 1, 9, 1, 7, 1, 1, 11, 1, 1, 1, 7, 1, 13, 3, 11, 5, 3, 1, 1, 15, 1, 13, 1, 11, 1, 1, 1, 17, 1, 5, 1, 13, 1, 11, 1, 1, 19, 3, 17, 1, 1, 7, 13, 1, 11, 1, 21, 1, 19, 1, 17, 1, 1, 1, 13, 1, 1, 23, 1, 7, 5, 19, 1, 17, 1, 1, 1, 13 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS G. C. Greubel, Rows n=1..100 of triangle, flattened FORMULA A093422(n,m)/A093423(n,m) = 2*binomial(n,m)*(m-1)!/(2*n-m+1) for 2 <= m < n. A093422(n,1)/A093423(n,1)= n. - R. J. Mathar, Apr 28 2007 EXAMPLE Triangle begins:   1;   1,  3;   1,  5,  1;   1,  7,  3,  5;   1,  9,  1,  7,  1;   1, 11,  1,  1,  1,  7;   1, 13,  3, 11,  5,  3,  1;   1, 15,  1, 13,  1, 11,  1,  1;   ... MAPLE A09342x := proc(n, m) local a, i, N, D ; N := n ; if m = 1 then D := 1 ; else D := n ; end ; for i from 1 to m-1 do N := N*(n-i) ; D := D+n-i ; od ; simplify(N/D) ; end: A093423 := proc(n, m) denom(A09342x(n, m)) ; end: for n from 1 to 12 do for m from 1 to n do printf("%d, ", A093423(n, m)) ; od ; od ; # R. J. Mathar, Apr 28 2007 MATHEMATICA Table[Denominator[2*Binomial[n, k]*(k-1)!/(2*n-k+1)], {n, 1, 30}, {k, 1, n}]//Flatten (* G. C. Greubel, Sep 01 2018 *) PROG (PARI) for(n=1, 10, for(k=1, n, print1(denominator(2*binomial(n, k)*(k-1)!/(2*n-k+1)), ", "))) \\ G. C. Greubel, Sep 01 2018 (MAGMA) /* as a triangle */ [[Denominator(2*Binomial(n, k)*Factorial(k-1)/(2*n-k+1)): k in [1..n]]: n in [1..30]]; // G. C. Greubel, Sep 01 2018 CROSSREFS Cf. A093412, A093413, A093414, A093415, A093417, A093418, A093419, A093420, A093421, A093422. Sequence in context: A305444 A002945 A171232 * A326454 A227507 A134700 Adjacent sequences:  A093420 A093421 A093422 * A093424 A093425 A093426 KEYWORD nonn,tabl,frac AUTHOR Amarnath Murthy, Mar 30 2004 EXTENSIONS More terms from R. J. Mathar, Apr 28 2007 Better definition from Omar E. Pol, Jan 10 2009 STATUS approved

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Last modified September 30 18:12 EDT 2020. Contains 337440 sequences. (Running on oeis4.)