A253254 - OEIS

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A253254

Largest prime factor of the n-th 11-gonal number.

2

11, 5, 29, 19, 47, 7, 13, 37, 83, 23, 101, 13, 17, 5, 137, 73, 31, 41, 173, 13, 191, 23, 19, 109, 227, 59, 7, 127, 263, 31, 281, 29, 23, 11, 317, 163, 67, 43, 353, 181, 53, 43, 389, 199, 37, 47, 17, 31, 443, 113, 461, 53, 479, 61, 71, 23, 103, 131, 41, 271, 31, 7, 569, 17, 587, 149, 17, 307, 89, 79

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OFFSET

2,1

COMMENTS

a(A024907(n)) = A061238(n).

LINKS

Robert Israel, Table of n, a(n) for n = 2..10000

FORMULA

a(n) = A006530(A051682(n)).

MAPLE

gpf:= n -> max(numtheory:-factorset(n));

seq(gpf(n*(9*n-7)/2), n=2..100); # Robert Israel, Jun 24 2015

PROG

(PARI) a(n) = my(f = factor(n*(9*n-7)/2)); f[#f~, 1]; \\ Michel Marcus, May 31 2015

CROSSREFS

Cf. A006530, A051682, A069902 (similar, with triangular numbers).

Sequence in context: A127820 A168206 A120831 * A373730 A363347 A229525

Adjacent sequences: A253251 A253252 A253253 * A253255 A253256 A253257

KEYWORD

nonn

AUTHOR

Gionata Neri, May 31 2015

STATUS

approved