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 A249743 #11 Nov 15 2014 16:48:47 %S A249743 1,8,34,90,208,376,628,816,1218,1768,2200,2922,3648,4342,5028,5988, %T A249743 7728,8478,10116,11572,12628,14298,16018,17710,21630,23128,24616, %U A249743 26856,28666,30622,35686,38382,42606,44062,50212,52698,56362,60798,63960,68680,73210,76200,82702,85498,90028,92136,101068,109492,114180,119308,126052,133122 %N A249743 Main diagonal of square arrays A114881 and A249741. %C A249743 One less than the main diagonal of square arrays A083140 and A083221 formed from the sieve of Eratosthenes. %F A249743 a(1) = 1, a(n) = (A000040(n) * A000040(2*(n-1))) - 1. [Where A000040(n) gives the n-th prime, p_n]. %F A249743 a(n) = A083140(n,n) - 1 = A083221(n,n) - 1. %F A249743 a(n) = A083141(n+1)-1. [With the current starting offset 2 of A083141]. %o A249743 (Scheme) (define (A249743 n) (if (= 1 n) n (- (* (A000040 n) (A000040 (+ n n -2))) 1))) %Y A249743 One less than A083141. %Y A249743 Cf. A000040, A083140, A083221, A114881, A249741. %K A249743 nonn %O A249743 1,2 %A A249743 _Antti Karttunen_, Nov 15 2014