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 A354947 #34 Jan 29 2024 15:09:39 %S A354947 2,2,0,2,1,1,0,2,1,1,1,2,1,1,1,1,1,1,1,1,1,1,0,1,0,1,1,0,1,1,0,1,1,1, %T A354947 1,1,0,1,0,1,1,1,1,0,1,1,1,1,1,1,0,0,1,1,0,0,0,1,2,0,1,0,0,0,0,0,2,1, %U A354947 0,0,1,0,0,1,1,0,1,1,0,0,0,1,0,1,0,1,1,0 %N A354947 Number of primes adjacent to prime(n) in a hexagonal spiral of positive integers. %H A354947 Dimitri Tishchenko, <a href="https://koozdra.wordpress.com/2011/09/30/hexagon-prime-spiral/">Hexagon Prime Spiral</a> %e A354947 The spiral begins %e A354947 13--12--11 %e A354947 / \ %e A354947 14 4---3 10 %e A354947 / / \ \ %e A354947 15 5 1---2 9 %e A354947 \ \ / %e A354947 16 6---7---8 %e A354947 \ %e A354947 17--18--19--... %e A354947 For n=4, prime(4) = 7 in the spiral has a(4) = 2 primes adjacent (2 and 19). %Y A354947 Cf. A307011, A307013 (spiral coordinates), A056105 (spiral first spoke). %K A354947 nonn,easy %O A354947 1,1 %A A354947 _Wade Reece Eberly_, Sep 23 2022