[seqfan] conventions

Douglas McNeil d.mcneil at qmul.ac.uk
Mon Mar 30 15:18:32 CEST 2009

So I've been playing with parsing the description of a sequence to 
automatically verify parts of the OEIS.  Obviously most truly interesting 
sequences are out of reach, but then again truly interesting sequences are 
likely to be getting more attention anyway: the idea here is to babysit 
constants, recurrences, sequences with specified formulae, and sequences 
of the "n such that prime(n^2)-3 == 5 mod 7" sort.

Found a fair number of minor errors this way.  Two questions came up:

(1) One thing I've noticed is that in some of the decimal expansions, the 
last entries in the sequence correspond not to a slice of the infinite 
decimal expansion but to a version rounded to the number of digits given.

E.g. A003881 = pi/4.  The OEIS sequence ends 9,2,6,7,0, which is its 
rounded version of the group of digits 92669955.

This rounding seems a little strange to me, as it makes sequences 
dependent on the number of entries.  When possible (which it usually is) 
I'd have expected the terms to be the same as in the infinite case.
Is this intended, or an accidental side effect of doing "Digits:=100; 
evalf(Pi/4);" in maple or the equivalent?

(2) In OEIS-world, what do round(1/2) and round(3/2) correspond to?


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