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 A127329 #33 Sep 19 2024 21:59:02 %S A127329 15,21,33,39,51,57,69,87,93,111,123,129,141,159,177,183,201,213,219, %T A127329 237,249,267,291,303,309,321,327,339,381,393,411,417,447,453,471,489, %U A127329 501,519,537,543,573,579,591,597,633,669,681,687,699,717,723,753,771,789 %N A127329 Semiprimes equal to the sum of three primes in arithmetic progression. %F A127329 Conjecture: a(n) = 3*A000040(n+2). - _Zak Seidov_, Jun 28 2015 %F A127329 Every member of the sequence is 3 times a prime; it is believed that every prime >= 5 arises in this way. This is related to Goldbach's conjecture: see comments to A078611. - _Robert Israel_ and _Michel Marcus_, Jun 28 2015 %e A127329 a(1) = 15 because 15 = 3 + 5 + 7; %e A127329 a(2) = 21 because 21 = 3 + 7 + 11. %o A127329 (Magma) [3*NthPrime(n+2): n in [1..60]]; // _Vincenzo Librandi_, Jun 28 2015, assuming the conjecture holds %Y A127329 Cf. A000040, A001358, A078611. %K A127329 easy,nonn %O A127329 1,1 %A A127329 _Giovanni Teofilatto_, Mar 30 2007 %E A127329 Corrected (57 = 7+19+31, 87 = 5+29+53, etc. inserted) by _R. J. Mathar_, Apr 22 2010