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 A067549 #12 Feb 21 2018 04:43:05 %S A067549 2,5,22,140,1448,17856,291456,5338368,119102976,3371378688, %T A067549 102163230720,3708532408320,149444916019200,6320831260262400, %U A067549 292612319045222400,15301128319716556800,891900404470539878400,53771252059997208576000,3564336303465704718336000 %N A067549 Determinant of n X n matrix whose diagonal are the first n primes and all other elements are 1's. %H A067549 Iain Fox, <a href="/A067549/b067549.txt">Table of n, a(n) for n = 1..300</a> %e A067549 The matrix begins: %e A067549 2 1 1 1 1 1 1 ... %e A067549 1 3 1 1 1 1 1 ... %e A067549 1 1 5 1 1 1 1 ... %e A067549 1 1 1 7 1 1 1 ... %e A067549 1 1 1 1 11 1 1 ... %e A067549 1 1 1 1 1 13 1 ... %p A067549 d:=(i,j)->`if`(i<>j,1,ithprime(i)): %p A067549 seq(LinearAlgebra[Determinant](Matrix(n,d)),n=1..20); # _Muniru A Asiru_, Feb 16 2018 %t A067549 Table[ Det[ DiagonalMatrix[ Table[ Prime[ i ] - 1, {i, 1, n} ] ] + 1 ], {n, 1, 20} ] %o A067549 (PARI) a(n) = matdet(matrix(n, n, i, j, if(i == j, prime(i), 1))) \\ _Iain Fox_, Feb 15 2018 %K A067549 nonn %O A067549 1,1 %A A067549 _Robert G. Wilson v_, Jan 28 2002 %E A067549 a(18)-a(19) from _Iain Fox_, Feb 15 2018