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Nontrivial Delannoy numbers that are primes.
2

%I #5 Mar 30 2012 18:50:48

%S 13,41,61,113,181,313,421,613,761,1013,1201,1289,1301,1741,1861,2113,

%T 2381,2521,3121,3613,4513,5101,5641,7321,8581,9661,9941,10513,11969,

%U 12641,13613,14281,14621,15313,16381,19013,19801,20201,21013,21841

%N Nontrivial Delannoy numbers that are primes.

%C Let D and T be defined as in A008288: then D(n,1)=D(1,n)=T(n,1)=T(n,n-1)=2*n+1, therefore all odd primes are Delannoy numbers; the sequence contains only primes of form D(n,k) with n>1 and k>1, resp. T(n,k) with 2<=k<=n-2.

%C apart from the first term A092830 is a subsequence.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/DelannoyNumber.html">Delannoy Number</a>

%e D(2,7)=T(9,2)=113=A000040(30), therefore 113 is a term.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Dec 03 2004