# Hartley's formula

Hartley's formula to determine the amount of information contained in a message with length n.

As Wikipedia tells us, Hartley's formula determines the amount of information contained in a message of length n.

That is, we have an alphabet A of which letters we make up a message:

The number of possible variants of different messages:

where N — the possible number of different messages; m — number of letters in the alphabet; n — the number of letters in a message.

Then the Hartley's formula is defined as:

,

where I — the amount of information, bits.

The Hartley's formula was proposed by Ralph Hartley in 1928 as one of the scientific approaches for message evaluation.

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