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A047204 Numbers that are congruent to {3, 4} mod 5. 22
3, 4, 8, 9, 13, 14, 18, 19, 23, 24, 28, 29, 33, 34, 38, 39, 43, 44, 48, 49, 53, 54, 58, 59, 63, 64, 68, 69, 73, 74, 78, 79, 83, 84, 88, 89, 93, 94, 98, 99, 103, 104, 108, 109, 113, 114, 118, 119, 123, 124, 128, 129, 133, 134, 138, 139, 143, 144, 148, 149 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also numbers that cannot be expressed as the sum of two 4th powers. - Cino Hilliard, Nov 23 2003

The sequence lists the indices of the multiples of 5 in A033567. - Bruno Berselli, Jan 05 2018

LINKS

Table of n, a(n) for n=1..60.

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

FORMULA

a(n) = 5*n - a(n-1) - 3 for n>1, a(1)=3. - Vincenzo Librandi, Nov 18 2010

G.f.: x*(3 + x + x^2) / ((1 + x)*(x - 1)^2). - R. J. Mathar, Oct 08 2011

a(n) = floor(5*n/2) - (-1)^n. - Wesley Ivan Hurt, Sep 12 2017

MATHEMATICA

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

PROG

(PARI) a(n)=(n-1)\2*5+4-n%2 \\ Charles R Greathouse IV, Dec 22 2011

CROSSREFS

Cf. A033567.

Sequence in context: A310017 A191285 A219658 * A050035 A306901 A046974

Adjacent sequences:  A047201 A047202 A047203 * A047205 A047206 A047207

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified February 20 08:00 EST 2020. Contains 332069 sequences. (Running on oeis4.)