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A047385 Numbers that are congruent to {2, 5} mod 7. 8
2, 5, 9, 12, 16, 19, 23, 26, 30, 33, 37, 40, 44, 47, 51, 54, 58, 61, 65, 68, 72, 75, 79, 82, 86, 89, 93, 96, 100, 103, 107, 110, 114, 117, 121, 124, 128, 131, 135, 138, 142, 145, 149, 152, 156, 159, 163, 166, 170 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also, numbers n such that (n^2+3)/7 is a nonnegative integer. - Bruno Berselli, Jan 16 2016

LINKS

Table of n, a(n) for n=1..49.

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

G.f.: x*(2 + 3*x + 2*x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Dec 05 2011

a(n) = (14*n - (-1)^n - 7)/4. - Bruno Berselli, Dec 05 2011

a(n) = 4*n - 2 - floor(n/2). - Wesley Ivan Hurt, Oct 16 2013

MAPLE

A047385:=n->4*n-2-floor(n/2); seq(A047385(k), k=1..100); # Wesley Ivan Hurt, Oct 16 2013

MATHEMATICA

Table[4 n - 2 - Floor[n/2], {n, 100}] (* Wesley Ivan Hurt, Oct 16 2013 *)

#+{2, 5}&/@(7*Range[0, 30])//Flatten (* Harvey P. Dale, Jul 15 2017 *)

PROG

(PARI) a(n)=(14*n-6)>>2 \\ Charles R Greathouse IV, Dec 05 2011

CROSSREFS

Sequence in context: A184922 A189461 A190506 * A284624 A086814 A211274

Adjacent sequences:  A047382 A047383 A047384 * A047386 A047387 A047388

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified July 23 11:34 EDT 2021. Contains 346259 sequences. (Running on oeis4.)