login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A138339
Smallest index in A138343 which starts a plateau of n consecutive integers.
9
OFFSET
1,2
COMMENTS
The sequence provides an indication of regions of nearly no improvements of the sequence of convergents to Pi when measured by the count of correct digits after rounding. A "plateau" of n consecutive integers is defined by a(n) = j such that A138343(j) = A138343(j+n-1) and such that none of the intermediate A138343 with index j+1 up to j+n-2 drop below this level.
EXAMPLE
a(3)=4 because the A138343(4) to A138343(6) are the earliest plateau of length 3.
The fact that there is a local maximum at A138343(5)=9 above the plateau is consistent with the definition.
CROSSREFS
KEYWORD
nonn,less,base,bref
AUTHOR
Artur Jasinski, Mar 16 2008
EXTENSIONS
Definition and values adapted to redefined A138343 - R. J. Mathar, Oct 01 2009
STATUS
approved