This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A129752 #5 Oct 18 2020 22:24:55 %S A129752 15,21,45,105,231,351,465,741,861,1431,1485,3081,3321,4005,7875,10731, %T A129752 11175,11781,13695,14535,17205,17391,18915,21321,22155,23871,30135, %U A129752 33411,36585,39621,42195,51681,58311,80601,90525,92235,97461,108345 %N A129752 Triangular numbers t which are average of two consecutive primes p and p+4. %C A129752 All terms are multiples of 3. %H A129752 Robert Israel, <a href="/A129752/b129752.txt">Table of n, a(n) for n = 1..10000</a> %F A129752 t-/+2 are pair of consecutive primes. %e A129752 15-/+2=(13,17), 21-/+2=(19,23), 45-/+2=(43,47) are pairs of consecutive primes. %p A129752 select(t -> isprime(t-2) and isprime(t+2), [seq(i*(i+1)/2,i=1..1000)]); # _Robert Israel_, Oct 18 2020 %Y A129752 Cf. A000217, A024675, A130178. %K A129752 nonn %O A129752 1,1 %A A129752 _Zak Seidov_, May 14 2007