[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?
Doug
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