[seqfan] A000021: Number of positive integers <= 2^n of form x^2 + 12 y^2.
Ed Jeffery
lejeffery7 at gmail.com
Sat Apr 14 18:50:23 CEST 2012
Hello,
A000021 = {1, 1, 2, 2, 6, 9, 17, 30, 54} (offset 0,3).
For this sequence, are we counting representations (or partitions)? If so,
then the example for n = 4 is
"EXAMPLE a(4)=6 since 2^4=16 and 1=1^2, 4=2^2, 9=3^2, 12=12*1^2,
13=1^2+12*1^2, 16=4^2,"
but we also have
16 = 2^2 + 12*1^2,
with the set of distinct pairs then being
{(1,0), (2,0), (3,0), (0,1), (1,1), (2,1), (4,0)}
of order 7. So I have to ask:
Should a(4) = 7?
Are the other terms of this sequence correct?
More information about the SeqFan
mailing list