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A084078 Length of list created by n substitutions k -> Range[ -Abs[k+1],Abs[k-1],2] starting with {0}. 1
1, 2, 4, 10, 24, 66, 172, 498, 1360, 4066, 11444, 34970, 100520, 312066, 911068, 2862562, 8457504, 26824386, 80006116, 255680170, 768464312, 2471150402, 7474561164, 24161357010, 73473471344, 238552980386, 728745517972 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..26.

FORMULA

see Mathematica line.

EXAMPLE

{0}, {-1,1}, {0,2,-2,0}, {-1,1,-3,-1,1,-1,1,3,-1,1}

MATHEMATICA

2 Rest@CoefficientList[InverseSeries[Series[(-1-6n-8n^2+(1+2n)^2 Sqrt[1+4n])/(2(n+4n^2+4n^3)), {n, 0, 28}]], n] from a(2) onwards, or Length/@Flatten/@NestList[ # /. k_Integer:>Range[ -Abs[k+1], Abs[k-1]]&, {1}, 8]

CROSSREFS

a(2n-1)=A027307, a(n)=2*A084075.

Sequence in context: A121704 A049144 A049131 * A137842 A049146 A000682

Adjacent sequences:  A084075 A084076 A084077 * A084079 A084080 A084081

KEYWORD

nonn

AUTHOR

Wouter Meeussen, May 11 2003

STATUS

approved

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Last modified August 24 05:52 EDT 2019. Contains 326260 sequences. (Running on oeis4.)