A108355 Expansion of (1+2x^2)/((1-x)^2(1+x^2)^2).

1, 2, 3, 4, 4, 4, 6, 8, 7, 6, 9, 12, 10, 8, 12, 16, 13, 10, 15, 20, 16, 12, 18, 24, 19, 14, 21, 28, 22, 16, 24, 32, 25, 18, 27, 36, 28, 20, 30, 40, 31, 22, 33, 44, 34, 24, 36, 48, 37, 26, 39, 52, 40, 28, 42, 56, 43, 30, 45, 60, 46, 32, 48, 64, 49, 34, 51, 68, 52, 36, 54, 72, 55

Offset

0,2

Comments

Row sums of triangle A108358.

Links

Table of n, a(n) for n=0..72.

Index entries for linear recurrences with constant coefficients, signature (2, -3, 4, -3, 2, -1).

Formula

a(n)=2a(n-1)-3a(n-2)+4a(n-3)-3a(n-4)+2a(n-5)-a(n-6); a(n)=-cos(pi*n/2)/4+(1-n)*sin(pi*n/2)/4+(3n+5)/4; a(n)=sum{k=0..n, mod(sum{j=0..n-k, C(k, j)C(n-j, k)floor((j+2)/2)}, 2)}

Crossrefs

Sequence in context: A339363 A114212 A344351 * A346049 A057951 A076410

Adjacent sequences: A108352 A108353 A108354 * A108356 A108357 A108358

Keyword

easy,nonn

Author

Paul Barry, May 31 2005

Status

approved