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 A129273 G.f.: 1-q = Sum_{k>=0} a(k)*q^k * Faq(k+1,q)^2, where Faq(n,q) is the q-factorial of n. 0
 1, -1, 2, -7, 26, -95, 344, -1256, 4654, -17470, 66234, -253192, 974992, -3778966, 14729200, -57683066, 226806148, -894791874, 3540105138, -14039128725, 55786507642, -222047783006, 885073034920, -3532110787193, 14110281656038 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Eric Weisstein's World of Mathematics, q-Factorial from MathWorld. FORMULA G.f.: 1-q = Sum_{k>=0} a(k)*q^k*{ Product_{i=1..k+1} (1-q^i)/(1-q) }^2. 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)^2 begin as follows: k=0: 1; k=1: .. -1, -2,-1; k=2: ....... 2, 8, 16,.. 20,.. 16,... 8,.... 2; k=3: ......... -7,-42, -133, -294, -497,. -672, ...; k=4: ............. 26,. 208,. 884, 2652,. 6266, ...; k=5: .................. -95, -950,-5035,-18810, ...; k=6: ........................ 344, 4128, 26144, ...; k=7: ............................ -1256,-17584, ...; k=8: .................................... 4654, ...; Sums cancel along 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))))^2), n, q))} CROSSREFS Cf. A127926. Sequence in context: A087448 A289449 A188860 * A055988 A275013 A278351 Adjacent sequences:  A129270 A129271 A129272 * A129274 A129275 A129276 KEYWORD sign AUTHOR Paul D. Hanna, Apr 07 2007 STATUS approved

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Last modified February 20 12:38 EST 2019. Contains 320327 sequences. (Running on oeis4.)