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A047352 Numbers that are congruent to {0, 2} mod 7. 7
0, 2, 7, 9, 14, 16, 21, 23, 28, 30, 35, 37, 42, 44, 49, 51, 56, 58, 63, 65, 70, 72, 77, 79, 84, 86, 91, 93, 98, 100, 105, 107, 112, 114, 119, 121, 126, 128, 133, 135, 140, 142, 147, 149, 154, 156, 161, 163, 168, 170 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Numbers k such that k^2/7 + k*(k + 1)/14 = k*(3*k + 1)/14 is a nonnegative integer. - Bruno Berselli, Feb 14 2017
LINKS
FORMULA
a(n) = 7*n - a(n-1) - 12 with a(1)=0. Also: a(n) = a(n-1) + a(n-2) - a(n-3). - Vincenzo Librandi, Aug 05 2010
a(n+1) = Sum_{k>=0} A030308(n,k)*b(k) with b(0)=2 and b(k)=A005009(k-1) for k>0. - Philippe Deléham, Oct 17 2011
G.f.: x^2*(2 + 5*x)/((1 + x)*(1 - x)^2). - R. J. Mathar, Dec 04 2011
a(n) = floor((7/3)*floor(3*n/2)). - Clark Kimberling, Jul 04 2012
E.g.f.: 5 + ((14*x - 17)*exp(x) - 3*exp(-x))/4. - David Lovler, Aug 31 2022
MATHEMATICA
LinearRecurrence[{1, 1, -1}, {0, 2, 7}, 50] (* Harvey P. Dale, Oct 16 2022 *)
PROG
(PARI) forstep(n=0, 200, [2, 5], print1(n", ")) \\ Charles R Greathouse IV, Oct 17 2011
CROSSREFS
Sequence in context: A077470 A347370 A205559 * A184400 A074244 A190565
KEYWORD
nonn,easy
AUTHOR
STATUS
approved

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Last modified July 14 05:06 EDT 2024. Contains 374291 sequences. (Running on oeis4.)