ceil bug

["Jon Perry" <perry@globalnet.co.uk>]

Working upon A001399, I developed the formula:

s(n)=6*t(floor(n/6))+(n%6)*(floor(n/6)+1)

with t(n)=n*(n+1)/2

Due to a typing mistake, I inadvertently typed:

s=6*t(floor(n/6))+(n%6)*(floor(n/6)+1)

and Pari produced 1/12*n^2 + 1/2*n

Testing this doesn't produce the sequence in question, however:

for(i=1,20,print1(ceil(1/12*i^2+1/2*i)","))

does.

(There is an minor additional rule; a(6k)=s(n)+1.)

Jon Perry
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http://www.users.globalnet.co.uk/~perry/maths/
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