A127991 2*n^3 - 2*n + 9 divided by 3*largest prime factor.

1, 1, 1, 1, 1, 11, 1, 3, 21, 39, 1, 31, 1, 1, 1, 7, 297, 9, 351, 1, 1, 19, 91, 1, 101, 141, 51, 33, 37, 49, 1, 299, 37, 1, 3, 39, 21, 1, 11, 1, 19, 1, 31, 1071, 351, 9, 43, 1, 481, 11, 511, 83, 3, 3, 69, 1, 1, 91, 1, 19, 187, 39, 219, 417, 553, 37, 1, 1, 1, 1369, 117, 693, 423, 31

Offset

1,6

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = A127989(n)/(3*A006530(A127989(n))). - Amiram Eldar, Mar 13 2020

Mathematica

a = {}; Do[AppendTo[a, 2n^3 - 2n + 9], {n, 1, 300}]; b = {}; Do[c = FactorInteger[a[[n]]]; d = c[[Length[c]]]; AppendTo[b, a[[n]]/(3 d[[1]])], {n, 1, Length[a]}]; b

Prog

(PARI) gpf(n)=my(f=factor(n)[, 1]); if(n==1, 1, f[#f]);
a(n)=my(m=2*n^3-2*n+9); m/gpf(m)/3 \\ Charles R Greathouse IV, Mar 13 2020

Crossrefs

Cf. A127979, A127990, A127992.

Sequence in context: A010198 A307245 A204846 * A110305 A010199 A010200

Adjacent sequences: A127988 A127989 A127990 * A127992 A127993 A127994

Keyword

nonn,easy

Author

Artur Jasinski, Feb 10 2007

Status

approved