cp's OEIS Frontend

A063763 Composite integers k such that largest prime factor of k > sqrt(k).

%I A063763 #21 Oct 06 2024 09:16:09
%S A063763 6,10,14,15,20,21,22,26,28,33,34,35,38,39,42,44,46,51,52,55,57,58,62,
%T A063763 65,66,68,69,74,76,77,78,82,85,86,87,88,91,92,93,94,95,99,102,104,106,
%U A063763 110,111,114,115,116,117,118,119,122,123,124,129,130,133,134,136,138
%N A063763 Composite integers k such that largest prime factor of k > sqrt(k).
%C A063763 Subsequence of composite terms of A064052.
%H A063763 Ray Chandler, <a href="/A063763/b063763.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Harry J. Smith)
%t A063763 Select[ Range[ 2, 160 ], !PrimeQ[ # ] && FactorInteger[ # ] [[ -1, 1 ] ] > Sqrt[ # ] & ]
%o A063763 (PARI) { n=0; for (m=2, 10^9, f=vecmax(component(factor(m), 1)); if(!isprime(m) && f^2 > m, write("b063763.txt", n++, " ", m); if (n==1000, break)) ) } \\ _Harry J. Smith_, Aug 30 2009
%o A063763 (Python)
%o A063763 from math import isqrt
%o A063763 from sympy import primepi
%o A063763 def A063763(n):
%o A063763     def f(x): return int(n+x-sum(primepi(x//i)-primepi(i) for i in range(2,isqrt(x)+1)))
%o A063763     m, k = n, f(n)
%o A063763     while m != k: m, k = k, f(k)
%o A063763     return m # _Chai Wah Wu_, Oct 05 2024
%Y A063763 Cf. A006530, A063538, A063539, A063762.
%K A063763 nonn
%O A063763 1,1
%A A063763 _Robert G. Wilson v_, Aug 14 2001