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A047364
Numbers that are congruent to {3, 4, 5} mod 7.
1
3, 4, 5, 10, 11, 12, 17, 18, 19, 24, 25, 26, 31, 32, 33, 38, 39, 40, 45, 46, 47, 52, 53, 54, 59, 60, 61, 66, 67, 68, 73, 74, 75, 80, 81, 82, 87, 88, 89, 94, 95, 96, 101, 102, 103, 108, 109, 110, 115, 116, 117, 122, 123, 124, 129, 130, 131, 136, 137, 138, 143
OFFSET
1,1
FORMULA
G.f.: x*(3+x+x^2+2*x^3)/((1+x+x^2)*(x-1)^2). - R. J. Mathar, Dec 04 2011
From Wesley Ivan Hurt, Jun 08 2016: (Start)
a(n) = a(n-1) + a(n-3) - a(n-4) for n>4.
a(n) = (21*n-6-12*cos(2*n*Pi/3)+4*sqrt(3)*sin(2*n*Pi/3))/9.
a(3k) = 7k-2, a(3k-1) = 7k-3, a(3k-2) = 7k-4. (End)
MAPLE
A047364:=n->(21*n-6-12*cos(2*n*Pi/3)+4*sqrt(3)*sin(2*n*Pi/3))/9: seq(A047364(n), n=1..100); # Wesley Ivan Hurt, Jun 08 2016
MATHEMATICA
LinearRecurrence[{1, 0, 1, -1}, {3, 4, 5, 10}, 60] (* Harvey P. Dale, Dec 03 2014 *)
Flatten[# + {3, 4, 5} & /@ (7 Range[0, 20])] (* or *)
Select[Range[0, 150], MemberQ[{3, 4, 5}, Mod[#, 7]] &] (* Robert G. Wilson v, Sep 26 2016 *)
PROG
(Magma) [n : n in [0..150] | n mod 7 in [3..5]]; // Wesley Ivan Hurt, Jun 08 2016
(PARI) a(n)=(n-1)\3*7 + (n-1)%3 + 3 \\ Charles R Greathouse IV, Sep 26 2016
CROSSREFS
Sequence in context: A014463 A340015 A161983 * A274519 A139445 A185345
KEYWORD
nonn,easy
STATUS
approved