The Commuter Challenge

Create one or more “hidden sequence” puzzles. In a hidden sequence puzzle, a set of 4-6 items are arranged in a precise sequence, and the reader is challenged to identify what the sequence is. The sequence can make use of esoteric knowledge, popular culture references, or be based on pure logic — that’s entirely up to you.

Here are some examples, along with their rules:

1. Jimmy
2. Ron
3. George
4. Bill

(rule: first names of successive US presidents)

1. Animalia
2. Plantae
3. Protista
4. Fungi
5. Prokaryota

(rule: the five biological kingdoms, in order of formal recognition)

1. 30
2. 42
3. 56
4. 72
5. 90
6. 110

(rule: 5×6, 6×7, 7×8, etcetera)

Of course, the rules are pretty easy to spot in these examples. A more interesting sequence might be the first names of successive vice presidents. Or, the first names of the presidential candidates that lost successive elections. You are encouraged to create multiple sequences of varying levels of difficulty.

The Results

Ryan Finholm

1. 1
2. 8
3. 11
4. 18
5. 80
6. 81
7. 82
8. 83
9. rule: Integers that start with a vowel when spelled out

1. 1
2. 4
3. 7
4. 11
5. 14
6. 17
7. 41
8. 44
9. rule: Integers with no circles or arcs (in traditional fonts)

Brian Raiter

1. 2
2. 4
3. 9
4. 28
5. 125
6. 726
7. rule: n! + n — i.e. 1 + 1, 1×2 + 2, 1×2×3 + 3, up to 1×2×3×4×5×6 + 6

1. mercury
2. copper
3. n/a
4. iron
5. tin
6. lead
7. rule: the metals traditionally associated with the planets, in order from the sun

1. 1: 1
2. 2: 2
3. 3: 2
4. 4: 3
5. 5: 3
6. 6: 1
7. rule: the number of lines, straight or curved, in the simple representation of each numeral — thus, 1 and 6 both require a single line, 2 and 3 require two separate lines, and 4 and 5 involve three lines each

1. mostly
2. so
3. life
4. end
5. guide
6. rule: the shortest word — excluding articles, conjunction, and prepositions — from the titles of the books in Douglas Adams’s Hitchhiker series, in reverse order of publication

1. F
2. G
3. J
4. P
5. R
6. rule: asymmetric letters of the alphabet (that is, letters that have no rotational or reflective symmetry, in any of their standard forms)

1. New Year’s Day
2. Groundhog Day
3. Cinco de Mayo
4. Veteran’s Day
5. rule: American holidays/observances that take place on doubled dates — 01/01, 02/02, 05/05, 11/11

1. Γ
2. Δ
3. Θ
4. Λ
5. Ξ
6. Π
7. rule: letters of the Greek alphabet, omitting letters that have the same shape as a letter in the Roman alphabet

1. Sun
2. Moon
3. Ceres (and several other asteroids)
4. Pluto
5. rule: solar system bodies that were once considered planets, in chronological order of their reclassification

1. T
2. M
3. N
4. E
5. A
6. I
7. rule: the letters of Morse Code that are represented by one or two signals, in alphabetical order of their representation — i.e. dah, dah-dah, dah-dit, dit, dit-dah, dit-dit

1. Belgium
2. Madagascar
3. Canada
4. Suriname
5. Bosnia & Herzegovina
6. rule: countries whose two-letter codes are also the symbols of alkaline earth elements — Be = beryllium, Mg = magnesium, Ca = calcium, Sr = strontium, Ba = barium