Search: id:A128815
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%I A128815
%S A128815 1,2,4,5,7,11,13,14,16,19,20,23,26,32,37,40,49,53,56,58,61,65,68,70,74,
%T A128815 76,77,79,88,89,98,100,104,109,110,116,118,130,137,140,142,146,149,152,
%U A128815 154,160,161,163,166,167,172,175,187,188,191,193,202,205,208,214,217
%N A128815 Numbers n such that n-th and (n+2)th triangular numbers sum up to a prime.
%C A128815 Or, numbers n such that 3+3n+n^2 is prime.
%F A128815 Tr(n)+Tr(n+2) is prime; A000217(n)+A000217(n+2) is prime.
%e A128815 7 is a term because 7*8/2+9*10/2=73 is prime;
%e A128815 11 is a term because 11*12/2+13*14/2=157 is prime.
%t A128815 Select[Range[300],PrimeQ[3+3#+#^2]&]
%Y A128815 Cf. A000217.
%Y A128815 Sequence in context: A082741 A099522 A108464 this_sequence A056527 A147991 
               A033160
%Y A128815 Adjacent sequences: A128812 A128813 A128814 this_sequence A128816 A128817 
               A128818
%K A128815 nonn
%O A128815 1,2
%A A128815 Zak Seidov (zakseidov(AT)gmail.com), Apr 10 2007

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