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

2, 3, 2, 7, 11, 7, 11, 29, 37, 23, 7, 67, 79, 23, 53, 17, 137, 19, 43, 191, 211, 29, 127, 277, 43, 163, 11, 379, 37, 109, 233, 71, 23, 281, 149, 631, 29, 13, 53, 71, 821, 431, 113, 947, 991, 47, 541, 1129, 107, 613, 29, 1327, 197, 179, 743, 67, 1597, 827

Offset

2,1

Links

Colin Barker, Table of n, a(n) for n = 2..1000

Formula

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

Example

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

Prog

(PARI)
pg(m, n) = (n^2*(m-2)-n*(m-4))/2 \\ n-th m-gonal number
lpf(m) = vecmax(factorint(m)[, 1]) \\ Largest prime factor
a(n) = lpf(pg(n, n))
vector(100, n, n++; a(n))

Crossrefs

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

Sequence in context: A208930 A122076 A209774 * A170842 A014784 A048601

Adjacent sequences: A271319 A271320 A271321 * A271323 A271324 A271325

Keyword

nonn

Author

Colin Barker, Apr 04 2016

Status

approved