%I A124199
%S A124199 13,19,43,53,89,103,151,229,251,349,433,463,593,701,739,859,1033,1223,
%T A124199 1429,1483,1709,1889,1951,2143,2699,3001,3079,3319,3739,4003,4093,4463,
%U A124199 4751,5563,5669,6553,7019,7873,8513,9043,10009,10151,10729,11173,11779
%N A124199 Primes of the form k(k+1)/2-2 (i.e. two less than triangular numbers).
%e A124199 The (first five triangular numbers)-2 are: -1,1,4,8,13. So a(1)=13 is 
               the first prime of this form.
%t A124199 Pick[ #1, PrimeQ[ #1]]&[((1/2)*#1*(#1 + 1) - 2 & ) /@ Range[180]]
%Y A124199 Cf. A055472.
%Y A124199 Sequence in context: A029478 A102907 A096455 this_sequence A119869 A106904 
               A106903
%Y A124199 Adjacent sequences: A124196 A124197 A124198 this_sequence A124200 A124201 
               A124202
%K A124199 easy,nonn
%O A124199 1,1
%A A124199 Peter Pein (petsie(AT)dordos.net), Dec 07 2006