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 A359017 #13 Feb 16 2025 08:34:04 %S A359017 1,2,3,11,20,84,455,1364,10659,58695,254540,728364,13516580,133595384, %T A359017 812646120,5327923964,68971338435,838101203939,7588384207404, %U A359017 69322940121435,490005293940084 %N A359017 a(n) is the index of the smallest triangular number with exactly n distinct prime factors. %H A359017 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DistinctPrimeFactors.html">Distinct Prime Factors</a> %H A359017 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TriangularNumber.html">Triangular Number</a> %o A359017 (PARI) a(n) = my(k=1); while(omega(k*(k+1)/2) != n, k++); k; \\ _Michel Marcus_, Feb 26 2023 %Y A359017 Cf. A000217, A001221, A076550, A076551. %K A359017 nonn,more %O A359017 0,2 %A A359017 _Ilya Gutkovskiy_, Dec 12 2022 %E A359017 a(19)-a(20) from _Michael S. Branicky_, Feb 25 2023