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A047206 Numbers that are congruent to {1, 3, 4} mod 5. 21
1, 3, 4, 6, 8, 9, 11, 13, 14, 16, 18, 19, 21, 23, 24, 26, 28, 29, 31, 33, 34, 36, 38, 39, 41, 43, 44, 46, 48, 49, 51, 53, 54, 56, 58, 59, 61, 63, 64, 66, 68, 69, 71, 73, 74, 76, 78, 79, 81, 83, 84, 86, 88, 89, 91, 93, 94, 96, 98, 99, 101, 103, 104, 106, 108 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..65.

FORMULA

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

a(n) = +1*a(n-1) +1*a(n-3) -1*a(n-4).

a(n)= 1+(5*n)/3-(i*sqrt(3) * (-1/2+(i*sqrt(3))/2)^n)/9+(i*sqrt(3)* (-1/2-(i*sqrt(3))/2)^n)/9 - Stephen Crowley, Feb 11 2007

a(n) = floor((5*n-1)/3). [From Gary Detlefs,May 14 2011]

MATHEMATICA

Select[Range[0, 200], MemberQ[{1, 3, 4}, Mod[#, 5]] &] (* Vladimir Joseph Stephan Orlovsky, Feb 12 2012 *)

PROG

(MAGMA) [ n : n in [1..150] | n mod 5 in [1, 3, 4] ]; - Vincenzo Librandi, Mar 2011

(PARI) a(n)=(5*n-1)\3 \\ Charles R Greathouse IV, Jul 01 2013

CROSSREFS

Sequence in context: A182772 A059535 A061402 * A187474 A081031 A133280

Adjacent sequences:  A047203 A047204 A047205 * A047207 A047208 A047209

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified October 31 06:33 EDT 2014. Contains 248845 sequences.