A271322 - OEIS

%I #8 Apr 04 2016 11:07:17

%S 2,3,2,7,11,7,11,29,37,23,7,67,79,23,53,17,137,19,43,191,211,29,127,

%T 277,43,163,11,379,37,109,233,71,23,281,149,631,29,13,53,71,821,431,

%U 113,947,991,47,541,1129,107,613,29,1327,197,179,743,67,1597,827

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

%H Colin Barker, <a href="/A271322/b271322.txt">Table of n, a(n) for n = 2..1000</a>

%F a(n) = A006530(A060354(n)).

%e a(5) = 7 because A060354(5) = 35 = 5 * 7.

%o (PARI)

%o pg(m, n) = (n^2*(m-2)-n*(m-4))/2 \\ n-th m-gonal number

%o lpf(m) = vecmax(factorint(m)[, 1]) \\ Largest prime factor

%o a(n) = lpf(pg(n, n))

%o vector(100, n, n++; a(n))

%Y Cf. A006530, A060354, A271319, A271320, A271321.

%K nonn

%O 2,1

%A _Colin Barker_, Apr 04 2016