Dogecoin is a cryptocurrency with a focus on fun, generosity, and community. It is unlike many other blockchain projects in that it does not aim to solve any ambitious problems. Dogecoin was originally created as a meme coin and has gained a large following that use the coin (DOGE) as an internet tipping and fundraising system.
Although Dogecoin was first created as somewhat of a joke, it has a passionate community that has used the platform for a variety of purposes. The project has gained widespread publicity and DOGE is traded on many exchanges.

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Primecoin is a cryptocurrency based on finding prime numbers. Identifying prime numbers plays a central role in cryptography. Primecoin's unique Proof-of-Work (PoW) consensus mechanism is able to increase transaction speeds and improve energy efficiency.
The network searches for special prime number chains known as Cunningham chains and bi-twin chains, which are of interest in mathematical research.

Flash Coin is a cryptocurrency designed to be used for everyday transactions. Flash's blokchain has a delegate-based consensus model that depends on elected delegates to verify transactions. These delegates elect 25 Miners who create new blocks on the blockchain. Each miner is given a specific time where they can mine a block. The Flash Coin algorithm also introduces a concept called Consensus Height, which refers to the moment when more than half of elected miners have created a block on top of another block in the chain.