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A092259
Numbers that are congruent to {4, 8} mod 12.
7
4, 8, 16, 20, 28, 32, 40, 44, 52, 56, 64, 68, 76, 80, 88, 92, 100, 104, 112, 116, 124, 128, 136, 140, 148, 152, 160, 164, 172, 176, 184, 188, 196, 200, 208, 212, 220, 224, 232, 236, 244, 248, 256, 260, 268, 272, 280, 284, 292, 296, 304, 308, 316, 320, 328, 332
OFFSET
1,1
FORMULA
G.f.: 4*x*(1+x+x^2) / ( (1+x)*(x-1)^2 ).
a(n) = 4 * A001651(n).
Iff phi(n) = phi(3n/2), then n is in A069587. - Labos Elemer, Feb 25 2004
a(n) = 12*(n-1)-a(n-1) (with a(1)=4). - Vincenzo Librandi, Nov 16 2010
From Wesley Ivan Hurt, May 21 2016: (Start)
a(n) = a(n-1) + a(n-2) - a(n-3) for n>3.
a(n) = 6n - 3 - (-1)^n.
a(2n) = A017617(n-1) for n>1, a(2n-1) = A017569(n-1) for n>1.
a(n) = -a(1-n), a(n) = A092899(n) + 1 for n>0. (End)
Sum_{n>=1} (-1)^(n+1)/a(n) = Pi*sqrt(3)/36. - Amiram Eldar, Dec 30 2021
MAPLE
A092259:=n->6*n-3-(-1)^n: seq(A092259(n), n=1..100); # Wesley Ivan Hurt, May 21 2016
MATHEMATICA
Table[6n-3-(-1)^n, {n, 80}] (* Wesley Ivan Hurt, May 21 2016 *)
LinearRecurrence[{1, 1, -1}, {4, 8, 16}, 60] (* Harvey P. Dale, Oct 07 2021 *)
PROG
(Magma) [n : n in [0..400] | n mod 12 in [4, 8]]; // Wesley Ivan Hurt, May 21 2016
CROSSREFS
Fourth row of A092260.
Sequence in context: A312803 A312804 A306199 * A312805 A312806 A036693
KEYWORD
nonn,easy
AUTHOR
Giovanni Teofilatto, Feb 19 2004
EXTENSIONS
Edited and extended by Ray Chandler, Feb 21 2004
STATUS
approved