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 A303339 #8 Apr 23 2018 08:35:14 %S A303339 1,36,3240,9568125,48024900,7589181600,56495217870,70320436841655, %T A303339 70320436841655,15696858221890560,1298157862542190650, %U A303339 5996877118268400000,2043364250317598208000,88678944280899462664980,615491489313111203244375,1056447213455901684717300 %N A303339 a(n) is the largest triangular number that is prime(n)-smooth. %F A303339 a(n) = A000217(A002072(n)). %e A303339 The first prime is 2, and the only triangular number that is 2-smooth is 1, so a(1) = 1. %e A303339 The second prime is 3, and the only triangular numbers that are 3-smooth are 1, 3, 6 = 2 * 3, and 36 = 2^2 * 3^2, so a(2) = 2. %e A303339 The third prime is 5, and the only triangular numbers that are 5-smooth are the 3-smooth triangular numbers and 10 = 2 * 5, 15 = 3 * 5, 45 = 3^2 * 5, 120 = 2^3 * 3 * 5, 300 = 2^2 * 3 * 5^2, and 3240 = 2^3 * 3^4 * 5, so a(3) = 3240. %Y A303339 Cf. A000217, A002072. %K A303339 nonn %O A303339 1,2 %A A303339 _Jon E. Schoenfield_, Apr 22 2018