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A047348 Numbers that are congruent to {2, 4} mod 7. 5
2, 4, 9, 11, 16, 18, 23, 25, 30, 32, 37, 39, 44, 46, 51, 53, 58, 60, 65, 67, 72, 74, 79, 81, 86, 88, 93, 95, 100, 102, 107, 109, 114, 116, 121, 123, 128, 130, 135, 137, 142, 144, 149, 151, 156, 158, 163, 165, 170 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also, integer values of (n*(n+1)+1)/7. - Bruno Berselli, Jan 25 2013

LINKS

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

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

FORMULA

From R. J. Mathar, Dec 16 2009: (Start)

a(n) = a(n-1) + a(n-2) - a(n-3).

G.f.: x*(2+2*x+3*x^2)/((1+x)*(x-1)^2). (End)

a(n) = 7*floor((n-1)/2) + 3 + (-1)^n. - Gary Detlefs, Mar 02 2010

a(n) = 7*n - a(n-1) - 8 with n > 1, a(1)=2. - Vincenzo Librandi, Aug 05 2010

MAPLE

seq(7*floor((n-1)/2)+3 +(-1)^n, n=1..49); # Gary Detlefs, Mar 02 2010

MATHEMATICA

LinearRecurrence[{1, 1, -1}, {2, 4, 9}, 50] (* Harvey P. Dale, Aug 04 2016 *)

CROSSREFS

Sequence in context: A030194 A190494 A101255 * A186699 A093859 A266257

Adjacent sequences:  A047345 A047346 A047347 * A047349 A047350 A047351

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified November 14 14:43 EST 2019. Contains 329126 sequences. (Running on oeis4.)