21. The formula which is already in arithmetic progression ? 22. In the case of primes containing an arithmetic progression , Karatsuba proved that this limit is infinite. 23. As of 2011, the longest known arithmetic progression of " consecutive " primes has length 10. 24. Much of her work has focused on arithmetic progressions , in particular extensions of the Green Tao theorem. 25. The 30? 60? 90?triangle is the only right triangle whose angles are in an arithmetic progression . 26. An arithmetic progression is a sequence of numbers in which the difference between adjacent numbers remains constant. 27. The 3 : 4 : 5 triangles are the only right triangles with edges in arithmetic progression . 28. If you add a red 9, then the red 3, 6, and 9 are in arithmetic progression . 29. Linnik's theorem ( 1944 ) concerns the size of the smallest prime in a given arithmetic progression . 30. Note that in an arithmetic progression 1 + 2 + 3 + 4 + 5 = 15.
