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URL: https://oeis.org/A390220

⇱ A390220 - OEIS

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A390220
a(n) = Sum_{k=0..floor(n/2)} binomial(k,4*n-8*k).
3
1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 5, 1, 15, 1, 35, 1, 70, 2, 126, 10, 210, 46, 330, 166, 495, 496, 716, 1288, 1014, 3004, 1456, 6436, 2275, 12871, 4200, 24312, 9248, 43776, 22440, 75736, 55233, 126940, 131955, 208336, 301246, 340120, 655522, 564928, 1362935, 980629, 2718577
OFFSET
0,12
FORMULA
G.f.: (1-x^2)^3 / ((1-x^2)^4 - x^9).
a(n) = 4*a(n-2) - 6*a(n-4) + 4*a(n-6) - a(n-8) + a(n-9).
a(2*n) = A306752(n).
a(n) = A390221(n) - A390221(n-2).
PROG
(PARI) my(N=60, x='x+O('x^N)); Vec((1-x^2)^3/((1-x^2)^4-x^9))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Jan 19 2026
STATUS
approved