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 A243291 #15 Mar 04 2024 01:36:26 %S A243291 1,1,1,3,2,4,3,7,7,7,6,10,7,10,12,15,10,16,11,17,17,17,14,22,22,20,25, %T A243291 24,19,27,20,31,28,27,31,34,25,30,33,37,28,38,29,39,42,37,32,46,45,47, %U A243291 44,46,37,52,50,52,49,48,42,57,43,51,59,63,59,61,48,61,60 %N A243291 Difference between n and the index of its largest prime factor: a(n) = n - A061395(n). %C A243291 All terms are strictly positive because A006530(n) <= n, A049084(n) < n and thus A061395(n) < n. [As A061395(n) = A049084(A006530(n))]. %C A243291 Please see also the comments at A243289. %H A243291 Antti Karttunen, <a href="/A243291/b243291.txt">Table of n, a(n) for n = 1..8192</a> %F A243291 a(n) = n - A061395(n). %F A243291 For n > 1, a(2^n) = (2^n)-1. %t A243291 a[n_] := n - PrimePi[FactorInteger[n][[-1, 1]]]; Array[a, 100] (* _Amiram Eldar_, Mar 04 2024 *) %o A243291 (Scheme) (define (A243291 n) (- n (A061395 n))) %Y A243291 Cf. A006530, A049084, A061395, A243289, A243290. %K A243291 nonn %O A243291 1,4 %A A243291 _Antti Karttunen_, Jun 04 2014