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 A279083 #14 Jan 22 2017 21:40:50 %S A279083 1,3,4,6,8,12,16,18,20,24,28,30,32,36,40 %N A279083 Numbers k such that there exists at least one tetrahedral number with exactly k divisors. %C A279083 The only odd terms are 1, 3, and 45 (which correspond to the three positive tetrahedral numbers that are square, i.e., 1, 4, and 19600). It is easy to show that no term larger than 6 is semiprime. %C A279083 A tetrahedral number with exactly 42 divisors would have to be of the form p^6 * q^2 * r, with p, q, and r distinct primes; does such a tetrahedral number exist? %C A279083 A tetrahedral number with exactly 50 divisors would have to be of the form p^4 * q^4 * r, with p, q, and r distinct primes; does such a tetrahedral number exist? %C A279083 Additional terms < 200 include (but may not be limited to) 44, 45, 48, 52, 54, 56, 60, 64, 68, 72, 76, 80, 84, 88, 90, 92, 96, 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140, 144, 148, 150, 152, 156, 160, 162, 164, 168, 172, 176, 180, 184, 188, 192, 196 %Y A279083 Cf. A000292, A279081, A279082. %K A279083 nonn,more %O A279083 1,2 %A A279083 _Jon E. Schoenfield_, Jan 06 2017