A392552 Expansion of 1 / ((1-x)^2 - x^4)^2.

1, 4, 10, 20, 37, 68, 126, 232, 420, 748, 1318, 2308, 4023, 6980, 12054, 20728, 35515, 60664, 103340, 175600, 297704, 503656, 850460, 1433560, 2412573, 4054148, 6803298, 11402028, 19086465, 31914204, 53307530, 88954328, 148301324, 247027700, 411140514, 683751740

Offset

0,2

Links

Seiichi Manyama, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (4,-6,4,1,-4,2,0,-1).

Formula

a(n) = Sum_{k=0..floor(n/4)} (k+1) * binomial(n-2*k+3,n-4*k).

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) + a(n-4) - 4*a(n-5) + 2*a(n-6) - a(n-8).

Prog

(PARI) my(N=40, x='x+O('x^N)); Vec(1/((1-x)^2-x^4)^2)

Crossrefs

Cf. A024490, A292324.

Sequence in context: A301170 A188280 A295950 * A375164 A038420 A008254

Adjacent sequences: A392549 A392550 A392551 * A392553 A392554 A392555

Keyword

nonn,easy

Author

Seiichi Manyama, Jan 16 2026

Status

approved