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%I #10 Jul 13 2017 22:27:50
%S 5,11,41,71,83,281,383,1181,1601,2351,2633,3491,3833,4283,5783,6221,
%T 6791,8783,10301,10883,11633,12251,14033,15581,18341,26111,26801,
%U 30881,31883,34721,38231,41333,41621,42491,43961,46061,47591,53633,60383
%N Primes of the form (5+ a triangular number A000217).
%H Harvey P. Dale, <a href="/A159049/b159049.txt">Table of n, a(n) for n = 1..1000</a>
%e 11 is in the list because it is A000217(3)+5 and a prime. 41=36+5= A000217(8)+5 is a prime. 71=66+5=A000217(11)+5 is a prime.
%t s=0;lst={};Do[s+=n;p=s+5;If[PrimeQ[p],AppendTo[lst,p]],{n,0,7!}];lst
%t Select[Accumulate[Range[0,500]]+5,PrimeQ] (* _Harvey P. Dale_, Jul 08 2017 *)
%o (PARI) for(n=1,500, if(isprime(k=n*(n+1)/2 + 5), print1(k, ", "))) \\ _G. C. Greubel_, Jul 13 2017
%Y Cf. A055469, A055472, A159047, A159048
%K nonn,easy
%O 1,1
%A _Vladimir Joseph Stephan Orlovsky_, Apr 03 2009
%E Definition rephrased, _R. J. Mathar_, Apr 05 2009
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