369

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Number

$369$ (three hundred and sixty-nine) is:

$3^2 \times 41$

The number of distinct free octominoes

The magic constant of a magic square of order $9$, after $1$, $(5)$, $15$, $34$, $65$, $111$, $175$, $260$:

$369 = \ds \dfrac 1 9 \sum_{k \mathop = 1}^{9^2} k = \dfrac {9 \paren {9^2 + 1} } 2$

Also see

• 369 Octominoes

• Previous  ... Next: Number of Free Polyominoes
• Previous  ... Next: Magic Constant of Magic Square

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $35$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $35$