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 A335331 #16 Aug 28 2020 01:56:00 %S A335331 2,3,5,7,11,13,17,19,23,29,37,43,47,53,61,71,73,89,97,103,107,113,131, %T A335331 149,151,173,181,197,223,227,229,251,263,281,307,311,349,359,379,409, %U A335331 419,433,463,503,521,541,571,593,613,659,691,701,719,761,809,827,853,863 %N A335331 a(n) = prime(k) where k is the n-th 7-smooth number. %C A335331 At A110069 we look for numbers of the form n = (d_1 + d_2 + ... + d_k)*prime(d_1*d_2*...*d_k) where d_1 d_2 ... d_k is the decimal expansion of n. As the largest prime that can be among the digits of a base-10 number is 7, the product of digits is 7-smooth. Hence the factor prime(d_1*d_2*...*d_k) is a term from this sequence. As lots of numbers have a product of digits of, say, 210^4, it would help to know prime(210^4) in advance. That's a(5817) of this sequence as 210^4 is the 5817th 7-smooth number. Precomputing such numbers is a computational benefit. %H A335331 David A. Corneth, <a href="/A335331/b335331.txt">Table of n, a(n) for n = 1..8862</a> %Y A335331 Cf. A002473, A006988, A033844, A110069. %K A335331 nonn %O A335331 1,1 %A A335331 _David A. Corneth_, Jun 01 2020