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A127926 G.f.: 1-q = Sum_{k>=0} a(k)*q^k*Faq(k+1,q), where Faq(n,q) is the q-factorial of n. 2
1, -1, 1, -2, 4, -7, 11, -18, 35, -76, 166, -358, 775, -1686, 3638, -7716, 16108, -33349, 69022, -143605, 301179, -636932, 1355855, -2896168, 6186750, -13183426, 27988755, -59197443, 124824911, -262699256, 552438175, -1162010894, 2446434685, -5156873960 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..33.

FORMULA

G.f.: 1-q = Sum_{k>=0} a(k)*q^k*Product_{i=1..k+1} (1-q^i)/(1-q).

EXAMPLE

Define Faq(n,q) = Product_{i=1..n} (1-q^i)/(1-q) for n>0, Faq(0,q)=1.

Then coefficients of q in a(k)*q^k*Faq(k+1,q) begin as follows:

k=0: 1;

k=1: .. -1, -1;

k=2: ....... 1, 2, 2,. 1;

k=3: ......... -2,-6,-10,-12,-10,. -6,. -2;

k=4: ............. 4, 16, 36, 60,. 80,. 88,.. 80, ...;

k=5: ................ -7,-35,-98,-203,-343, -497, ...;

k=6: .................... 11, 66, 220, 539, 1078, ...;

k=7: ....................... -18,-126,-486,-1368, ...;

k=8: ............................. 35, 280, 1225, ...;

k=9: ................................. -76, -684, ...;

k=10: ...................................... 166, ...;

Sums cancel down column j for j>1, leaving 1-q.

PROG

(PARI) {a(n)=if(n==0, 1, polcoeff(1-q- sum(k=0, n-1, a(k)*q^k*prod(j=1, k+1, (1-q^j)/(1-q+q*O(q^(n-k))))), n, q))}

CROSSREFS

First column of A179750. [From Mats Granvik, Jul 26 2010]

Sequence in context: A239552 A023426 A157134 * A078513 A308871 A325546

Adjacent sequences:  A127923 A127924 A127925 * A127927 A127928 A127929

KEYWORD

sign

AUTHOR

Paul D. Hanna, Feb 06 2007

STATUS

approved

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Last modified July 18 01:14 EDT 2019. Contains 325110 sequences. (Running on oeis4.)