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A081256 Greatest prime factor of n^3 + 1. 19
2, 3, 7, 13, 7, 31, 43, 19, 73, 13, 37, 19, 157, 61, 211, 241, 13, 307, 7, 127, 421, 463, 13, 79, 601, 31, 37, 757, 271, 67, 19, 331, 151, 1123, 397, 97, 43, 67, 1483, 223, 547, 1723, 139, 631, 283, 109, 103, 61, 181, 43, 2551, 379, 919, 409, 2971, 79, 103, 3307, 163 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. J. Mathar and T. D. Noe, Table of n, a(n) for n = 1..10000 (first 5000 terms from R. J. Mathar)

FORMULA

a(n) = A006530(A001093(n)). - M. F. Hasler, Jun 13 2018

MAPLE

A081256 := proc(n)

    A006530(n^3+1) ;

end proc:

seq(A081256(n), n=1..20) ; # R. J. Mathar, Feb 13 2014

MATHEMATICA

Table[Max[Transpose[FactorInteger[n^3 + 1]][[1]]], {n, 25}]

PROG

(PARI) a(n)=my(f=factor(n^3+1)); f[#f~, 1] \\ Charles R Greathouse IV, Mar 08 2017

(PARI) A081256(n)=vecmax(factor(n^3+1)[, 1]) \\ It seems slightly slower to get the last element using ...[-1..-1][1]. - M. F. Hasler, Jun 15 2018

CROSSREFS

Cf. A081257, A081258.

Cf. A096173 n^3+1 is an odd semiprime, A096174 (n^3+1)/(n+1) is prime.

Cf. A006530, A001093.

Sequence in context: A249051 A225093 A278007 * A084955 A273056 A026472

Adjacent sequences:  A081253 A081254 A081255 * A081257 A081258 A081259

KEYWORD

easy,nonn

AUTHOR

Jan Fricke (fricke(AT)uni-greifswald.de), Mar 14 2003

EXTENSIONS

More terms from Harvey P. Dale, Mar 22 2003

More terms from Hugo Pfoertner, Jun 20 2004

STATUS

approved

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Last modified September 19 21:02 EDT 2018. Contains 315217 sequences. (Running on oeis4.)