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 A143836 #24 Mar 24 2023 17:48:12 %S A143836 4,5,6,7,8,9,8,9,10,12,10,11,12,14,15,11,12,13,15,16,18,13,14,15,17, %T A143836 18,20,21,16,17,18,20,21,23,24,26,17,18,19,21,22,24,25,27,30,20,21,22, %U A143836 24,25,27,28,30,33,34,22,23,24,26,27,29,30,32,35,36,39,23,24,25,27,28,30,31,33,36,37,40,42 %N A143836 Triangle read by rows: T(r,c) = (prime(r+2) + prime(c+1))/2. %C A143836 The number of appearances of m >= 1 in this sequence is A061357(m). Conjecture: Every integer >= 4 appears at least once in this sequence. - _Ya-Ping Lu_, Mar 05 2023 %C A143836 The number of composites between 3 and (r+2)-th prime missing from Row 1 through Row r in the triangle is A334810(r+2). - _Ya-Ping Lu_, Mar 24 2023 %e A143836 Triangle begins: %e A143836 4; %e A143836 5, 6; %e A143836 7, 8, 9; %e A143836 8, 9, 10, 12; %e A143836 10, 11, 12, 14, 15; %e A143836 ... %o A143836 (PARI) T(r,c) = (prime(r+2) + prime(c+1))/2; \\ _Michel Marcus_, Mar 07 2023 %Y A143836 Cf. A098090 (1st column, except 1st term), A024675 (right diagonal). %K A143836 nonn,tabl %O A143836 1,1 %A A143836 _Pierre CAMI_, Sep 02 2008 %E A143836 Name simplified by _Ya-Ping Lu_, Mar 05 2023