cp's OEIS Frontend

A271322 Largest prime factor of the n-th n-gonal number (A060354).

%I A271322 #8 Apr 04 2016 11:07:17
%S A271322 2,3,2,7,11,7,11,29,37,23,7,67,79,23,53,17,137,19,43,191,211,29,127,
%T A271322 277,43,163,11,379,37,109,233,71,23,281,149,631,29,13,53,71,821,431,
%U A271322 113,947,991,47,541,1129,107,613,29,1327,197,179,743,67,1597,827
%N A271322 Largest prime factor of the n-th n-gonal number (A060354).
%H A271322 Colin Barker, <a href="/A271322/b271322.txt">Table of n, a(n) for n = 2..1000</a>
%F A271322 a(n) = A006530(A060354(n)).
%e A271322 a(5) = 7 because A060354(5) = 35 = 5 * 7.
%o A271322 (PARI)
%o A271322 pg(m, n) = (n^2*(m-2)-n*(m-4))/2 \\ n-th m-gonal number
%o A271322 lpf(m) = vecmax(factorint(m)[, 1]) \\ Largest prime factor
%o A271322 a(n) = lpf(pg(n, n))
%o A271322 vector(100, n, n++; a(n))
%Y A271322 Cf. A006530, A060354, A271319, A271320, A271321.
%K A271322 nonn
%O A271322 2,1
%A A271322 _Colin Barker_, Apr 04 2016