A117411 Skew triangle associated to the Euler numbers.

1, 0, 1, 0, -4, 1, 0, 0, -12, 1, 0, 0, 16, -24, 1, 0, 0, 0, 80, -40, 1, 0, 0, 0, -64, 240, -60, 1, 0, 0, 0, 0, -448, 560, -84, 1, 0, 0, 0, 0, 256, -1792, 1120, -112, 1, 0, 0, 0, 0, 0, 2304, -5376, 2016, -144, 1, 0, 0, 0, 0, 0, -1024, 11520, -13440, 3360, -180, 1, 0, 0, 0, 0, 0, 0, -11264, 42240, -29568, 5280, -220, 1

Offset

0,5

Comments

Inverse is A117414. Row sums of the inverse are the Euler numbers A000364.

Triangle, read by rows, given by [0,-4,4,0,0,0,0,0,0,0,...] DELTA [1,0,1,0,0,0,0,0,0,0,...] where DELTA is the operator defined in A084938. - Philippe Deléham, Nov 01 2009

Links

G. C. Greubel, Rows n = 0..50 of the triangle, flattened

Formula

Sum_{k=0..n} T(n, k) = A006495(n).

Sum_{k=0..floor(n/2)} T(n-k, k) = A117413(n).

T(n, k) = (-4)^(n-k)*Sum_{j=0..n-k} C(n,k-j)*C(j,n-k).

G.f.: (1-x*y)/(1-2x*y+x^2*y(y+4)). - Paul Barry, Mar 14 2006

T(n, k) = (-4)^(n-k)*A098158(n,k). - Philippe Deléham, Nov 01 2009

T(n, k) = 2*T(n-1,k-1) - 4*T(n-2,k-1) - T(n-2,k-2), T(0,0) = T(1,1) = 1, T(1,0) = 0, T(n,k) = 0 if k > n or if k < 0. - Philippe Deléham, Oct 31 2013

From G. C. Greubel, Sep 07 2022: (Start)

T(n, n) = 1.

T(n, n-1) = -4*A000217(n-1), n >= 1.

T(n, n-2) = (-4)^2 * A000332(n), n >= 2.

T(n, n-3) = (-4)^3 * A000579(n), n >= 3.

T(n, n-4) = (-4)^4 * A000581(n), n >= 4.

T(2*n, n) = A262710(n). (End)

Example

Triangle begins
  1;
  0,  1;
  0, -4,   1;
  0,  0, -12,   1;
  0,  0,  16, -24,    1;
  0,  0,   0,  80,  -40,     1;
  0,  0,   0, -64,  240,   -60,      1;
  0,  0,   0,   0, -448,   560,    -84,      1;
  0,  0,   0,   0,  256, -1792,   1120,   -112,      1;
  0,  0,   0,   0,    0,  2304,  -5376,   2016,   -144,      1;
  0,  0,   0,   0,    0, -1024,  11520, -13440,   3360,   -180,    1;
  0,  0,   0,   0,    0,     0, -11264,  42240, -29568,   5280, -220,    1;
  0,  0,   0,   0,    0,     0,   4096, -67584, 126720, -59136, 7920, -264, 1;

Mathematica

T[n_, k_]:= T[n, k]= (-4)^(n-k)*Sum[Binomial[n, k-j]*Binomial[j, n-k], {j, 0, n-k}];
Table[T[n, k], {n, 0, 15}, {k, 0, n}]//Flatten (* G. C. Greubel, Sep 07 2022 *)

Prog

(Magma)
A117411:= func< n, k | (-4)^(n-k)*(&+[Binomial(n, k-j)*Binomial(j, n-k): j in [0..n-k]]) >;
[A117411(n, k): k in [0..n], n in [0..15]]; // G. C. Greubel, Sep 07 2022
(SageMath)
def A117411(n, k): return (-4)^(n-k)*sum(binomial(n, k-j)*binomial(j, n-k) for j in (0..n-k))
flatten([[A117411(n, k) for k in (0..n)] for n in (0..15)]) # G. C. Greubel, Sep 07 2022

Crossrefs

Cf. A000364, A006495 (row sums), A098158, A117413, A117414.

Cf. A000217, A000332, A000579, A000581, A262710.

Sequence in context: A334702 A345300 A085992 * A161739 A291574 A094924

Adjacent sequences: A117408 A117409 A117410 * A117412 A117413 A117414

Keyword

easy,sign,tabl

Author

Paul Barry, Mar 13 2006

Status

approved