Snakes in the Plane.Kekulé claimed that the structure of benzene appeared to him in a dream that included a snake eating its tail. (Ouroboros image and the benzene structural diagram,via Wikimedia Commons). |

Numbers represented on a seven-segment display. (Illustration by the author). |

• Integer sequence A001746, integers for which at least one character is a loop character, four excluded; e.g., 0, 6, 8, 9, 10, 16, 18, 19, 20, 26, 28, 29, 30, 36, 38, 39, 40, 46, 48, 49, 50...I was inspired enough by my brush with glory to compose two computer programs for finding such numbers. The first of which (holey_numbers.c) calculates the integer sequence

• Integer sequence A001745, as above, but with four included; e.g., 0, 4, 6, 8, 9, 10, 14, 16, 18, 19, 20, 24, 26, 28, 29, 30, 34, 36, 38, 39, 40, 44, 46, 48, 49, 50...

• Integer sequence A001743, integers for which every character is a loop character, four excluded; e.g., 0, 6, 8, 9, 60, 66, 68, 69, 80, 86, 88, 89, 90, 96, 98, 99, 600, 606, 608, 609, 660, 666, 668, 669, 680, 686, 688...

• Integer sequence A001744, integers for which every character is a loop character, four included; e.g., 0, 4, 6, 8, 9, 40, 44, 46, 48, 49, 60, 64, 66, 68, 69, 80, 84, 86, 88, 89, 90, 94, 96, 98, 99, 400...

Distribution of the holey numbers of integer sequence A001744 up to 10,000. This is the sequence in which all digits have loops, and it includes the digit "4." Note the huge wasteland from 1000 - 3999. Graphic by the author, via Gnumeric. |

- The On-Line Encyclopedia of Integer Sequences™ (OEIS™). At this writing, the OEIS contains 212,514 sequences.
- One reference to Faraday can be found at Henry A. Torrey, "Glimpses into the Structure of Molecules," Harper's Monthly Magazine, vol. 120, December, 1909 - May, 1910, pp.261-266. A reference to Franklin can be found at G.A. Bobrick, "Liquid Air," Journal of Electricity, Power and Gas, vol. 13, January-December, 1903, pp.368-372.