1,1

Such number digits after decimal point of number Pi where the approximation to the number Pi by a root of a polynomial of 2 degree does not improve the accuracy exactly n next digits

a(1)=18 because 3.141592653589793238 (18 digits) is root of -3061495+674903*x+95366*x^2 and 3.1415926535897932385 (19 digits) also is root of that same polynomial -3061495+674903*x+95366*x^2

Cf. A138335, A138337, A138338.

Adjacent sequences: A138333 A138334 A138335 this_sequence A138337 A138338 A138339

Sequence in context: A109911 A065751 A038632 this_sequence A166630 A154920 A094224

nonn,uned,probation

Artur Jasinski (grafix(AT)csl.pl), Mar 15 2008

There are comments in the entry for A138335 which may cast doubt on the validity of this and related sequences. - N. J. A. Sloane (njas(AT)research.att.com), Mar 19 2008