Search: id:A152900
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%I A152900
%S A152900 2,3,5,7,11,13,19,23,29,31,41,43,53,71,73,89,109,127,131,157,163,181,
%T A152900 211,233,239,241,271,281,307,379,419,421,431,461,463,541,599,601,613,
%U A152900 701,743,757,811,827,929,977,991,1123,1259,1481,1483,1559,1721,1723
%N A152900 Primes p such that there exists a triangular number t with p*t also triangular.
%C A152900 Sequence A152899 contains the triangular numbers t.
%H A152900 T. D. Noe, <a href="b152900.txt">Table of n, a(n) for n=1..1000</a>
%e A152900 11 is here because 21 and 11*21 are triangular.
%t A152900 TriQ[n_]:=IntegerQ[Sqrt[1+8n]]; Select[Prime[Range[1000]], TriQ[2#-1] 
               || TriQ[2#+1] || TriQ[(#-1)/2] || TriQ[(#+1)/2] &]
%Y A152900 A000217
%Y A152900 Sequence in context: A097375 A007459 A129944 this_sequence A079151 A005728 
               A049643
%Y A152900 Adjacent sequences: A152897 A152898 A152899 this_sequence A152901 A152902 
               A152903
%K A152900 nonn
%O A152900 1,1
%A A152900 T. D. Noe (noe(AT)sspectra.com), Dec 14 2008

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