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 A335603 #9 Oct 09 2020 17:02:01 %S A335603 0,1,2,2,3,2,4,3,4,3,5,4,6,4,3,4,7,4,8,6,4,5,9,6,6,6,6,8,10,3,11,5,5, %T A335603 7,4,4,12,8,6,9,13,4,14,10,6,9,15,8,8,6,7,12,16,6,5,12,8,10,17,6,18, %U A335603 11,8,6,6,5,19,14,9,4,20,6,21,12,6,16,5,6,22,12 %N A335603 a(n) = p*q where p is the sequential number (or PrimePi, A000720) of the largest prime divisor of n, and q is the maximal exponent in the canonical representation of n (A051903). %C A335603 a(n) is like a real-valued footprint of n. %H A335603 Alois P. Heinz, <a href="/A335603/b335603.txt">Table of n, a(n) for n = 1..10000</a> %F A335603 a(n) = A000720(A006530(n)) * A051903(n). - _Alois P. Heinz_, Jun 11 2020 %p A335603 with(numtheory): %p A335603 a:= n-> pi(max(factorset(n)))*max(0, seq(i[2], i=ifactors(n)[2])): %p A335603 seq(a(n), n=1..100); # _Alois P. Heinz_, Jun 11 2020 %t A335603 a[n_] := PrimePi[(f = FactorInteger[n])[[-1, 1]]] * Max[f[[;; , 2]]]; Array[a, 100] (* _Amiram Eldar_, Jun 11 2020 *) %o A335603 (PARI) a(n) = if (n==1, 0, my(f=factor(n)); primepi(vecmax(f[, 1]))*vecmax(f[, 2])); \\ _Michel Marcus_, Jun 11 2020 %Y A335603 Cf. A000720, A006530, A051903. %Y A335603 A076526 is a similar "footprint" of n. %K A335603 nonn %O A335603 1,3 %A A335603 _Todor Szimeonov_, Jun 11 2020 %E A335603 Edited by _N. J. A. Sloane_, Jun 15 2020