A117442 - OEIS

%I #31 Mar 10 2024 15:11:31

%S 1,-1,1,3,-2,1,-11,9,-3,1,57,-44,18,-4,1,-361,285,-110,30,-5,1,2763,

%T -2166,855,-220,45,-6,1,-24611,19341,-7581,1995,-385,63,-7,1,250737,

%U -196888,77364,-20216,3990,-616,84,-8,1,-2873041,2256633,-885996,232092,-45486,7182,-924,108,-9,1

%N Number triangle read by rows, related to exp(x)/(cos(x) + sin(x)).

%H G. C. Greubel, <a href="/A117442/b117442.txt">Rows n = 0..50 of the triangle, flattened</a>

%F T(n, 0) = (-1)^n*A001586(n).

%F Sum_{k=0..n} T(n, k) = A117443(n).

%F Column k has e.g.f. (x^k/k!)/(cos(x) + sin(x)).

%F Apart from signs the T(n,k) are the coefficients of the polynomials p(n, x) = 2^n*Sum_{k=0..n} binomial(n,k)*euler(k)*((x+1)/2)^(n-k). - _Peter Luschny_, Jun 08 2013

%F From _G. C. Greubel_, Jun 02 2021: (Start)

%F T(n, k) = (-1)^(n+k) * binomial(n, k) * abs(numerator( Euler(n-k, 1/4) )), where Euler(n, x) is the Euler number polynomial.

%F T(n, n) = 1.

%F T(n, n-1) = -A000027(n) = -binomial(n+1, 1).

%F T(n, n-2) = A045943(n+1) = 3*binomial(n+2, 2).

%F T(n, n-3) = -A111080(n) = -11*binomial(n+3, 3).

%F T(j, k) = (-1)^k * binomial(j+k, k) * abs(numerator( Euler(k, 1/4) )) (columns).

%F T(n, n-j) = (-1)^n * binomial(n+j, j) * abs(numerator( Euler(n, 1/4) )) (downward diagonals). (End)

%F The pair of triangles P*((I + P^4)/2)^(-1) and P^3*((I + P^4)/2)^(-1), where P denotes Pascal's triangle A007318, give the present triangle but with a different pattern of signs. - _Peter Bala_, Mar 07 2024

%e Triangle begins

%e        1;

%e       -1,     1;

%e        3,    -2,     1;

%e      -11,     9,    -3,    1;

%e       57,   -44,    18,   -4,    1;

%e     -361,   285,  -110,   30,   -5,  1;

%e     2763, -2166,   855, -220,   45, -6,  1;

%e   -24611, 19341, -7581, 1995, -385, 63, -7, 1;

%p A117442_row := proc(n) 2^n*add(binomial(n,k)*euler(k)*((x+1)/2)^(n-k), k=0..n);

%p seq((-1)^(n-j)*abs(coeff(%,x,j)),j=0..n) end:

%p seq(print(A117442_row(n)),n=0..5);  # _Peter Luschny_, Jun 08 2013

%t row[n_] := row[n] = 2^n Sum[Binomial[n, k] EulerE[k] ((x+1)/2)^(n-k), {k, 0, n}];

%t T[n_, k_] := (-1)^(n-k) Abs[Coefficient[row[n], x, k]];

%t Table[T[n, k], {n, 0, 9}, {k, 0, n}] (* _Jean-François Alcover_, Jun 13 2019, from Maple *)

%t Table[(-1)^(n-k)*Binomial[n, k]*Abs[Numerator[EulerE[n-k, 1/4]]], {n, 0, 12}, {k, 0, n}]//Flatten (* _G. C. Greubel_, Jun 02 2021 *)

%o (PARI) E(n) = 2^n*2^(n+1)*(subst(bernpol(n+1, x), x, 3/4) - subst(bernpol(n+1, x), x, 1/4))/(n+1); \\ A122045

%o p(n) = 2^n*sum(k=0, n, binomial(n,k)*E(k)*((x+1)/2)^(n-k));

%o row(n) = my(rp=p(n)); vector(n+1, k, k--; (-1)^(n-k)*abs(polcoeff(rp, k))); \\ _Michel Marcus_, Nov 16 2020

%o (Sage)

%o def f(n): return (1/4)^n*sum( binomial(n, j)*2^j*euler_number(j) for j in (0..n)) # f(n) = Euler(n, 1/4)

%o def A117442(n,k): return (-1)^(n+k)*binomial(n,k)*abs(numerator(f(n-k)))

%o flatten([[A117442(n,k) for k in (0..n)] for n in (0..12)]) # _G. C. Greubel_, Jun 02 2021

%Y Inverse of A117440.

%Y Second column contains A161722 as subsequence.

%Y Cf. A000027, A001586, A045943, A111080, A122045, A117443 (row sums).

%K easy,sign,tabl

%O 0,4

%A _Paul Barry_, Mar 16 2006