A047287 - OEIS

A047287

Numbers that are congruent to {0, 1, 2, 3, 6} mod 7.

0, 1, 2, 3, 6, 7, 8, 9, 10, 13, 14, 15, 16, 17, 20, 21, 22, 23, 24, 27, 28, 29, 30, 31, 34, 35, 36, 37, 38, 41, 42, 43, 44, 45, 48, 49, 50, 51, 52, 55, 56, 57, 58, 59, 62, 63, 64, 65, 66, 69, 70, 71, 72, 73, 76, 77, 78

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OFFSET

1,3

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,1,-1).

FORMULA

G.f.: x^2*(1+x+x^2+3*x^3+x^4)/((1-x)^2*(1+x+x^2+x^3+x^4)). [Colin Barker, May 14 2012]

a(n) = a(n-1) + a(n-5) - a(n-6) for n > 6. - Vincenzo Librandi, May 15 2012

a(n) = (7*n - 5 - 2*(n mod 5))/5. - Wesley Ivan Hurt, Dec 28 2016

MATHEMATICA

Select[Range[0, 400], MemberQ[{0, 1, 2, 3, 6}, Mod[#, 7]]&] (* Vincenzo Librandi, May 15 2012 *)

PROG

(Magma) I:=[0, 1, 2, 3, 6, 7]; [n le 6 select I[n] else Self(n-1)+Self(n-5)-Self(n-6): n in [1..70]]; // Vincenzo Librandi, May 15 2012

CROSSREFS

Sequence in context: A265334 A050019 A163099 * A039047 A372439 A336205

Adjacent sequences: A047284 A047285 A047286 * A047288 A047289 A047290

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved