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A152020
Denominator of 8/(9n^2) divided by 9.
1
1, 1, 9, 2, 25, 9, 49, 8, 81, 25, 121, 18, 169, 49, 225, 32, 289, 81, 361, 50, 441, 121, 529, 72, 625, 169, 729, 98, 841, 225, 961, 128, 1089, 289, 1225, 162, 1369, 361, 1521, 200, 1681, 441, 1849, 242, 2025, 529, 2209, 288, 2401, 625
OFFSET
1,3
FORMULA
a(n) = A152018(n)/9.
a(1)=1, a(2)=1, a(3)=9, a(4)=2, a(5)=25, a(6)=9, a(7)=49, a(8)=8, a(9)=81, a(10)=25, a(11)=121, a(12)=18, a(n)=3*a(n-4)-3*a(n-8)+a(n-12). - Harvey P. Dale, Aug 25 2013
Conjecture: a(n) = denominator((n-2)^3/n^2). - Andres Cicuttin, Sep 19 2017
a(n) = n^2/gcd(n^2, 8). - Andrew Howroyd, Jul 25 2018
Sum_{n>=1} 1/a(n) = Pi^2/3 (A195055). - Amiram Eldar, Sep 14 2022
MATHEMATICA
Denominator[8/(9*Range[50]^2)]/9 (* or *) LinearRecurrence[{0, 0, 0, 3, 0, 0, 0, -3, 0, 0, 0, 1}, {1, 1, 9, 2, 25, 9, 49, 8, 81, 25, 121, 18}, 50] (* Harvey P. Dale, Aug 25 2013 *)
PROG
(PARI) a(n) = denominator(8/(9*n^2))/9 \\ Michel Marcus, Jun 01 2013
CROSSREFS
Sequence in context: A272033 A356356 A098289 * A055516 A248314 A174837
KEYWORD
nonn,mult
AUTHOR
Paul Curtz, Nov 20 2008
EXTENSIONS
More terms from Michel Marcus, Jun 01 2013
Keyword:mult added by Andrew Howroyd, Jul 25 2018
STATUS
approved