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A025248

a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ... + a(n-3)*a(3) for n >= 4, with initial terms 1, 0, 2, 2.

1, 0, 2, 2, 2, 6, 14, 26, 58, 142, 326, 754, 1826, 4438, 10750, 26378, 65354, 162334, 405046, 1016546, 2561074, 6472550, 16415086, 41761786, 106526810, 272411054, 698275622, 1793763282, 4617047618, 11906277750, 30757124830, 79582907370, 206231537770

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..33.

FORMULA

G.f.: (1+x-sqrt(1-2*x+x^2-8*x^3))/2. - Michael Somos, Jun 08 2000

Conjecture: n*a(n) +(-2*n+3)*a(n-1) +(n-3)*a(n-2) +4*(-2*n+9)*a(n-3)=0. - R. J. Mathar, Feb 25 2015

PROG

(PARI) a(n)=polcoeff((x-sqrt(1-2*x+x^2-8*x^3+x*O(x^n)))/2, n)

CROSSREFS

Sequence in context: A257255 A248765 A007039 * A213170 A321741 A101416

Adjacent sequences: A025245 A025246 A025247 * A025249 A025250 A025251

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

URL: https://oeis.org/A025248

⇱ A025248 - OEIS