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Template:Sequence of the Day for April 24

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Intended for: April 24, 2013

Timetable

  • First draft entered by Alonso del Arte on March 19, 2012
  • Draft reviewed by Daniel Forgues on April 26, 2012
  • Draft approved by Alonso del Arte on January 12, 2013
Yesterday's SOTD * Tomorrow's SOTD

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A187677: Primes of the form
8 n 2 + 6 n  −  1
.
221 223 225 227 229 231 233 235
219 145 147 149 151 153 155 157
217 143 85 87 89 91 93 95
215 141 83 41 43 45 47 49
213 139 81 39 13 15 17 19
211 137 79 37 11 1 3 21
209 135 77 35 9 7 5 23

In a variant of the Ulam spiral in which only odd numbers are entered, some primes still line up along some diagonals but not others. Without the even numbers, primes can also line up in horizontal and diagonal lines. This sequence comes from an upwards vertical line which starts with 13.