308

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Number

$308$ (three hundred and eight) is:

$2^2 \times 7 \times 11$

The $7$th heptagonal pyramidal number after $1$, $8$, $26$, $60$, $115$, $196$:

$308 = 1 + 7 + 18 + 34 + 55 + 81 + 112 = \dfrac {7 \paren {7 + 1} \paren {5 \times 7 - 2} } 6$

The $51$st nontotient:

$\nexists m \in \Z_{>0}: \map \phi m = 308$

where $\map \phi m$ denotes the Euler $\phi$ function

Also see

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