A227293 G.f.: sqrt( Sum_{n>=0} 4^n*x^(n^2) ).

1, 2, -2, 4, -2, 12, -36, 104, -330, 1068, -3356, 10808, -35156, 115192, -380744, 1267152, -4242778, 14285644, -48336684, 164272984, -560515836, 1919455464, -6594719992, 22725877680, -78531331524, 272062125048, -944738639640, 3287748182064, -11464667424744, 40053463412080, -140178051713680, 491396601445280

Offset

0,2

Links

Table of n, a(n) for n=0..31.

Example

 G.f.: A(x) = 1 + 2*x - 2*x^2 + 4*x^3 - 2*x^4 + 12*x^5 - 36*x^6 + 104*x^7 - 330*x^8 + 1068*x^9 - 3356*x^10 + 10808*x^11 - 35156*x^12 +...
where
A(x)^2 = 1 + 4*x + 4^2*x^4 + 4^3*x^9 + 4^4*x^16 + 4^5*x^25 + 4^6*x^36 +...

Prog

 (PARI) {a(n)=polcoeff(sqrt(sum(k=0, n, 4^k*x^(k^2))+x*O(x^n)), n)}
for(n=0, 36, print1(a(n), ", "))

Crossrefs

Sequence in context: A137777 A126984 A159749 * A331391 A359442 A102416

Adjacent sequences: A227290 A227291 A227292 * A227294 A227295 A227296

Keyword

sign

Author

Paul D. Hanna, Jul 05 2013

Status

approved