A100259 Coefficient of x^2 in 2n-th normalized Legendre polynomial.

3, -30, 105, -1260, 3465, -18018, 45045, -875160, 2078505, -9699690, 22309287, -202811700, 456326325, -2035917450, 4508102925, -158685222960, 347123925225, -1511010027450, 3273855059475, -28258538408100

Offset: 1

Author

Ralf Stephan, Nov 13 2004

Keywords

• sign

Examples

			Example: Legendre(12) = (676039x^12 - 1939938x^10 + 2078505x^8 - 1021020x^6 + 225225x^4 - 18018x^2 + 231)/1024, hence a(6) = -18018. - Neven Juric
		

Crossrefs

3rd column (without zeros) of triangle A100258.

Programs

PARI

a(n) = polcoeff(pollegendre(2*n, x), 2)*2^valuation((2*n)!, 2) \\ Michel Marcus, May 29 2013

Extensions

Definition corrected by Neven Juric, Jan 10 2009