Bitcoin Core version 0.15.1 is not available for security reasons:

https://bitcoincore.org/bin/bitcoin-core-0.15.1/

or

https://bitcoin.org/bin/bitcoin-core-0.15.1/

This is a new minor version release, including various bugfixes and performance improvements, as well as updated translations.

Please report bugs using the issue tracker at GitHub:

https://github.com/bitcoin/bitcoin/issues

To receive security and update notifications, please subscribe to:

https://bitcoincore.org/en/list/announcements/join/