ID | Description / Title |

**151**
| Paper sheets of standard sizes: an expected-value problem |

**152**
| Writing 1/2 as a sum of inverse squares |

**153**
| Investigating Gaussian Integers |

**154**
| Exploring Pascal's pyramid |

**155**
| Counting Capacitor Circuits |

**156**
| Counting Digits |

**157**
| Solving the diophantine equation ^{1}/_{a}+^{1}/_{b}= ^{p}/_{10n} |

**158**
| Exploring strings for which only one character comes lexicographically after its neighbour to the left |

**159**
| Digital root sums of factorisations |

**160**
| Factorial trailing digits |

**161**
| Triominoes |

**162**
| Hexadecimal numbers |

**163**
| Cross-hatched triangles |

**164**
| Numbers for which no three consecutive digits have a sum greater than a given value |

**165**
| Intersections |

**166**
| Criss Cross |

**167**
| Investigating Ulam sequences |

**168**
| Number Rotations |

**169**
| Exploring the number of different ways a number can be expressed as a sum of powers of 2 |

**170**
| Find the largest 0 to 9 pandigital that can be formed by concatenating products |

**171**
| Finding numbers for which the sum of the squares of the digits is a square |

**172**
| Investigating numbers with few repeated digits |

**173**
| Using up to one million tiles how many different "hollow" square laminae can be formed? |

**174**
| Counting the number of "hollow" square laminae that can form one, two, three, ... distinct arrangements |

**175**
| Fractions involving the number of different ways a number can be expressed as a sum of powers of 2 |

**176**
| Right-angled triangles that share a cathetus |

**177**
| Integer angled Quadrilaterals |

**178**
| Step Numbers |

**179**
| Consecutive positive divisors |

**180**
| Rational zeros of a function of three variables |

**181**
| Investigating in how many ways objects of two different colours can be grouped |

**182**
| RSA encryption |

**183**
| Maximum product of parts |

**184**
| Triangles containing the origin |

**185**
| Number Mind |

**186**
| Connectedness of a network |

**187**
| Semiprimes |

**188**
| The hyperexponentiation of a number |

**189**
| Tri-colouring a triangular grid |

**190**
| Maximising a weighted product |

**191**
| Prize Strings |

**192**
| Best Approximations |

**193**
| Squarefree Numbers |

**194**
| Coloured Configurations |

**195**
| Inscribed circles of triangles with one angle of 60 degrees |

**196**
| Prime triplets |

**197**
| Investigating the behaviour of a recursively defined sequence |

**198**
| Ambiguous Numbers |

**199**
| Iterative Circle Packing |

**200**
| Find the 200th prime-proof sqube containing the contiguous sub-string "200" |