A090855 a(n) is the least positive integer such that the integer part of the arithmetic-geometric mean of a(n) and 1 is equal to 2^n.

1, 4, 10, 24, 55, 127, 288, 640, 1408, 3069, 6642, 14281, 30544, 65028, 137896, 291399, 613885, 1289715, 2702909, 5652038, 11795170, 24570079, 51095155, 106092067, 219972452, 455493427, 942031726, 1946056082, 4015916211

Offset

0,2

Links

Table of n, a(n) for n=0..28.

Formula

floor( agm(a(n), 1) ) = 2^n, for n>=0.

Mathematica

Flatten[{1, Table[Ceiling[y /. FindRoot[Log[Pi/(2*EllipticK[1 - y^2])] == n*Log[2], {y, n*2^n}, MaxIterations -> 1000]], {n, 1, 50}]}] (* Vaclav Kotesovec, Sep 28 2019 *)

Crossrefs

Cf. A090852, A090854, A090856.

Sequence in context: A273228 A291727 A291224 * A052252 A087447 A129953

Adjacent sequences: A090852 A090853 A090854 * A090856 A090857 A090858

Keyword

nonn

Author

Paul D. Hanna, Dec 10 2003

Status

approved