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 A054523 Triangle read by rows: T(n,k) = phi(n/k) if k divides n, T(n,k)=0 otherwise (n >= 1, 1 <= k <= n). 37
 1, 1, 1, 2, 0, 1, 2, 1, 0, 1, 4, 0, 0, 0, 1, 2, 2, 1, 0, 0, 1, 6, 0, 0, 0, 0, 0, 1, 4, 2, 0, 1, 0, 0, 0, 1, 6, 0, 2, 0, 0, 0, 0, 0, 1, 4, 4, 0, 0, 1, 0, 0, 0, 0, 1, 10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 4, 2, 2, 2, 0, 1, 0, 0, 0, 0, 0, 1, 12, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 6, 6 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS From Gary W. Adamson, Jan 08 2007: (Start) Let H be this lower triangular matrix. Then: H * A051731 = A126988, H * [1, 2, 3, ...] = 1, 3, 5, 8, 9, 15, ... = A018804, H * sigma(n) = A038040 = d(n) * n = 1, 4, 6, 12, 10, ... where sigma(n) = A000203, H * d(n) (A000005) = sigma(n) = A000203, Row sums of H = A018804 = sum of GCD (k,n), H^2 * d(n) = d(n)*n, H^2 = A127192, H * mu(n) (A008683) = phi(n) = A000010, H^2 row sums = A018804. (End) The Möbius inversion principle of Richard Dedekind and Joseph Liouville (1857), cf. "Concrete Mathematics", p. 136, is equivalent to the statement that row sums are the row index n. - Gary W. Adamson, Aug 03 2008 The multivariable row polynomials give n times the cycle index for the cyclic group C_n, called Z(C_n) (see the MathWorld link with the Harary reference):   n*Z(C_n) = Sum_{k=1..n} T(n,k)*(y_{n/k})^k, n >= 1.   E.g., 6*Z(C_6) = 2*(y_6)^1 + 2*(y_3)^2 + 1*(y_2)^3 + 1*(y_1)^6. - Wolfdieter Lang, May 22 2012 See A102190 for the array without zeros, and reversed rows. - Wolfdieter Lang, May 29 2012 This is the number of permutations in the n-th cyclic group which are the product of k disjoint cycles. - Robert A. Beeler, Aug 09 2013 REFERENCES Ronald L. Graham, D. E. Knuth, Oren Patashnik, Concrete Mathematics, Addison-Wesley, 2nd ed., 1994, p. 136. [Gary W. Adamson, Aug 03 2008] LINKS Reinhard Zumkeller, Rows n = 1..125 of triangle, flattened Eric Weisstein's World of Mathematics, Cycle Index. FORMULA Equals A054525 * A126988 as infinite lower triangular matrices. - Gary W. Adamson, Aug 03 2008 EXAMPLE Triangle begins    1;    1, 1;    2, 0, 1;    2, 1, 0, 1;    4, 0, 0, 0, 1;    2, 2, 1, 0, 0, 1;    6, 0, 0, 0, 0, 0, 1;    4, 2, 0, 1, 0, 0, 0, 1;    6, 0, 2, 0, 0, 0, 0, 0, 1;    4, 4, 0, 0, 1, 0, 0, 0, 0, 1;   10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1;    4, 2, 2, 2, 0, 1, 0, 0, 0, 0, 0, 1; MAPLE A054523 := proc(n, k) if n mod k = 0 then numtheory[phi](n/k) ; else 0; end if; end proc: # R. J. Mathar, Apr 11 2011 MATHEMATICA T[n_, k_] := If[Divisible[n, k], EulerPhi[n/k], 0]; T[1, 1] = 1; Table[T[n, k], {n, 1, 10}, {k, 1, n}]//Flatten (* G. C. Greubel, Dec 15 2017 *) PROG (Haskell) a054523 n k = a054523_tabl !! (n-1) !! (k-1) a054523_row n = a054523_tabl !! (n-1) a054523_tabl = map (map (\x -> if x == 0 then 0 else a000010 x)) a126988_tabl -- Reinhard Zumkeller, Jan 20 2014 (PARI) for(n=1, 10, for(k=1, n, print1(if(!(n % k), eulerphi(n/k), 0), ", "))) \\ G. C. Greubel, Dec 15 2017 CROSSREFS Cf. A054521, A054525, A102190. Sequence in context: A292047 A292049 A320341 * A161363 A293136 A106351 Adjacent sequences:  A054520 A054521 A054522 * A054524 A054525 A054526 KEYWORD nonn,tabl AUTHOR N. J. A. Sloane, Apr 09 2000 STATUS approved

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Last modified September 19 04:52 EDT 2019. Contains 327187 sequences. (Running on oeis4.)