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 A155897 #6 Apr 20 2013 04:52:39 %S A155897 0,1,1,0,1,1,1,0,1,1,1,0,0,1,0,1,0,1,1,0,1,0,0,0,0,0,1,1,0,0,0,0,1,0, %T A155897 1,0,1,0,1,0,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,0,0,0,0,0,0,0,1,1,0,0,0, %U A155897 0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,1,1,0,1,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,1,0 %N A155897 Square matrix T(m,n)=1 if (2m+1)^n-2 is prime, 0 otherwise; read by antidiagonals. %C A155897 In some sense a "minimal" possible generalization of the pattern of Mersenne primes (cf. A000043) is to consider powers of odd numbers (> 1) minus 2. Since even powers obviously correspond to an odd power of the base squared, it is sufficient to consider only odd powers, cf. A155899. %o A155897 (PARI) T = matrix( 19,19,m,n, isprime((2*m+1)^n-2)) ; %o A155897 A155897 = concat( vector( vecmin( matsize(T)), i, vector( i, j, T[j,i-j+1]))) %Y A155897 Cf. A084714, A128472, A094786, A014224, A109080, A090669, A128455, A128457, A128458, A128459, A128460, A128461. %K A155897 easy,nonn,tabl %O A155897 1,1 %A A155897 _M. F. Hasler_, Feb 01 2009