A049139 Revert transform of (1 - x - 2x^2 + x^3)/(1 - 2x^2).

1, 1, 2, 6, 20, 72, 272, 1063, 4262, 17432, 72448, 305074, 1298812, 5581188, 24175560, 105448157, 462745106, 2041634108, 9050879192, 40296196096, 180099939464, 807757872276, 3634378951656, 16399912908504, 74201196229816

Offset

1,3

Links

Table of n, a(n) for n=1..25.

Index entries for reversions of series

Formula

Recurrence: 49*(n-2)*(n-1)*n*(324*n^4 - 4896*n^3 + 27331*n^2 - 66829*n + 60376)*a(n) = 14*(n-2)*(n-1)*(6480*n^5 - 107640*n^4 + 693860*n^3 - 2158612*n^2 + 3214669*n - 1809319)*a(n-1) - 4*(n-2)*(14256*n^6 - 272448*n^5 + 2120024*n^4 - 8564544*n^3 + 18871769*n^2 - 21420614*n + 9740185)*a(n-2) - 16*(3240*n^7 - 73260*n^6 + 705778*n^5 - 3754269*n^4 + 11895329*n^3 - 22403869*n^2 + 23150751*n - 10079360)*a(n-3) - 16*(n-4)*(n-2)*(2592*n^5 - 46944*n^4 + 325028*n^3 - 1067288*n^2 + 1640321*n - 921819)*a(n-4) + 128*(n-5)*(n-4)*(2*n - 11)*(324*n^4 - 3600*n^3 + 14587*n^2 - 25559*n + 16306)*a(n-5). - Vaclav Kotesovec, Jan 02 2021

Mathematica

Rest[CoefficientList[InverseSeries[Series[x*(1 - x - 2x^2 + x^3)/(1 - 2x^2), {x, 0, 40}], x], x]] (* Vaclav Kotesovec, Jan 02 2021 *)

Crossrefs

Sequence in context: A049129 A063376 A161168 * A071356 A141200 A186996

Adjacent sequences: A049136 A049137 A049138 * A049140 A049141 A049142

Keyword

nonn

Author

Olivier Gérard

Status

approved