This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
def fill(rows, queens, leftattack, notdownattack, rightattack, color):
global c
available = ~leftattack & notdownattack & ~rightattack & color
if rows==1:
if available==0:
c[queens] = c.get(queens, 0) + 1
else:
c[queens+1] = c.get(queens+1, 0) + bin(available).count('1')
return
while available:
attack = available & -available
fill(rows-1, queens+1, (leftattack|attack)<<1, notdownattack&~attack, (rightattack|attack)>>1, ~color)
available &= available - 1
fill(rows-1, queens, leftattack<<1, notdownattack, rightattack>>1, ~color)
print(' n a(n) count')
for n in range(1, 32):
c=dict()
fill(n, 0, 0, (1<
See A352426.
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