285

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Number

$285$ (two hundred and eighty-five) is:

$3 \times 5 \times 19$

The $9$th square pyramidal number after $1$, $5$, $14$, $30$, $55$, $91$, $140$, $204$:

$285 = 1 + 4 + 9 + 16 + 25 + 36 + 49 + 64 + 81 = \ds \sum_{k \mathop = 1}^9 k^2 = \dfrac {9 \paren {9 + 1} \paren {2 \times 9 + 1} } 6$

The $16$th integer after $7$, $13$, $19$, $35$, $38$, $41$, $57$, $65$, $70$, $125$, $130$, $190$, $205$, $223$, $253$ the decimal representation of whose square can be split into two parts which are each themselves square:

$285^2 = 81 \, 225$; $81 = 9^2$, $225 = 15^2$

The $30$th sphenic number after $30$, $42$, $66$, $70$, $\ldots$, $182$, $186$, $190$, $195$, $222$, $230$, $231$, $246$, $255$, $258$, $266$, $273$, $282$:

$285 = 3 \times 5 \times 19$

The $53$rd lucky number:

$1$, $3$, $7$, $9$, $13$, $15$, $21$, $\ldots$, $219$, $223$, $231$, $235$, $237$, $241$, $259$, $261$, $267$, $273$, $283$, $285$, $\ldots$

The $56$th positive integer $n$ such that no factorial of an integer can end with $n$ zeroes.

Also see

• Previous  ... Next: Square Pyramidal Number
• Previous  ... Next: Squares whose Digits can be Separated into 2 other Squares
• Previous: Numbers of Zeroes that Factorial does not end with

No further terms of this sequence are documented on $\mathsf{Pr} \infty \mathsf{fWiki}$.

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