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A108623 G.f. satisfies x = (A(x)-(A(x))^2)/(1-A(x)-(A(x))^2). 3
1, 0, -1, -1, 1, 4, 3, -8, -23, -10, 67, 153, 9, -586, -1081, 439, 5249, 7734, -7941, -47501, -53791, 105314, 430119, 343044, -1249799, -3866556, -1730017, 13996097, 34243897, 1947204, -150962373, -296101864, 121857185, 1582561870 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

Row sums of inverse of Riordan array (1/(1-x-x^2), x(1-x)/(1-x-x^2)) (Cf. A053538). - Paul Barry, Nov 01 2006

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

FORMULA

Binomial transform of A105523. - Paul Barry, Nov 01 2006

G.f.: (1+x-sqrt(1-2x+5x^2))/(2(1-x)). - Paul Barry, Nov 01 2006

Conjecture: n*a(n) +3*(1-n)*a(n-1) +(7*n-18)*a(n-2) +5*(3-n)*a(n-3)=0. - R. J. Mathar, Nov 15 2011

Lim sup n->infinity |a(n)|^(1/n) = sqrt(5). - Vaclav Kotesovec, Feb 08 2014

Series reversion of g.f. of A212804. - Michael Somos, May 19 2014

G.f.: x / (1 - x + x /(1 - x / (1 - x + x / (1 - x / ...)))). - Michael Somos, May 19 2014

0 = a(n)*(25*a(n+1) - 50*a(n+2) + 45*a(n+3) - 20*a(n+4)) + a(n+1)*(-20*a(n+1) + 34*a(n+2) - 44*a(n+3) + 25*a(n+4) + a(n+2)*(12*a(n+2) - 2*a(n+3) - 6*a(n+4) + a(n+3)*(a(n+4)) if n>=0. - Michael Somos, May 19 2014

EXAMPLE

G.f. = x - x^3 - x^4 + x^5 + 4*x^6 + 3*x^7 - 8*x^8 - 23*x^9 - 10*x^10 + ...

MATHEMATICA

CoefficientList[Series[(1+x-Sqrt[1-2*x+5*x^2])/(2*x*(1-x)), {x, 0, 20}], x] (* Vaclav Kotesovec, Feb 08 2014 *)

a[ n_] := SeriesCoefficient[ (1 + x - Sqrt[1 - 2 x + 5 x^2]) / (2 (1 - x)), {x, 0, n}]; (* Michael Somos, May 19 2014 *)

a[ n_] := If[ n < 1, 0, SeriesCoefficient[ InverseSeries[ Series[ (x - x^2) / (1 - x - x^2), {x, 0, n}]], {x, 0, n}]]; (* Michael Somos, May 19 2014 *)

PROG

(PARI) {a(n) = if( n<0, 0, polcoeff( (1 + x - sqrt(1 - 2*x + 5*x^2 + x^2 * O(x^n))) / (2 * (1 - x)), n))}; /* Michael Somos, May 19 2014 */

(PARI) {b(n) = if( n<1, 0, polcoeff( serreverse( (x - x^2) / (1 - x - x^2) + x * O(x^n)), n))}; /* Michael Somos, May 19 2014 */

CROSSREFS

Cf. A039978. Except for signs, same as A108624.

Cf. A105523, A212804.

Sequence in context: A320263 A215330 A108624 * A248248 A159550 A279386

Adjacent sequences:  A108620 A108621 A108622 * A108624 A108625 A108626

KEYWORD

sign

AUTHOR

Christian G. Bower, Jun 12 2005

STATUS

approved

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Last modified May 5 23:41 EDT 2021. Contains 343579 sequences. (Running on oeis4.)