This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A278694 #8 Apr 07 2020 21:53:03 %S A278694 2,3,5,7,11,19,23,29,59,61,73,83,163,167,173,181,191,223,487,491,509, %T A278694 547,569,653,659,677,709,1459,1481,1487,1531,1621,1949,2027,2111,4397, %U A278694 4447,4457,4547,4597,4861,4943,5051,5861,6323,6563 %N A278694 Primes p such that every suffix of the ternary (base-3) representation of p is either a prime or 1. %C A278694 All numbers are of one of the following forms base 3: %C A278694 a. 10...02, where there are 0 or more 0's %C A278694 b. 20...0x, where x is a, b, or 1, and there are 0 or more 0's %C A278694 c. 10 %C A278694 d. 2 %e A278694 11 is in the sequence, since 11=102_3 and the base-3 suffix 2_3 is 2, which is prime. %e A278694 659 is in the sequence, since 659=220102_3, and the base-3 suffixes are 20102_3=173, 102_3=11, and 2_3=2, all of which are prime. %K A278694 nonn,base %O A278694 1,1 %A A278694 _Randy L. Ekl_, Nov 26 2016