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A047406 Numbers that are congruent to {4, 6} mod 8. 7
4, 6, 12, 14, 20, 22, 28, 30, 36, 38, 44, 46, 52, 54, 60, 62, 68, 70, 76, 78, 84, 86, 92, 94, 100, 102, 108, 110, 116, 118, 124, 126, 132, 134, 140, 142, 148, 150, 156, 158, 164, 166, 172, 174, 180, 182, 188, 190, 196, 198, 204, 206, 212, 214, 220, 222, 228 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

In groups of four, add the odd and even numbers (4=1+3, 6=2+4; 12=5+7, 14=6+8; etc.). - George E. Antoniou, Dec 12 2001

The first 250 terms (4 through 998) are the 250 non-occurring Fibonacci number residues modulo 1000; i.e., if leading zeros are supplied as necessary for the terms having fewer than three digits, these are the 250 sets of three digits that never appear as the last three digits of a Fibonacci number. - Jon E. Schoenfield, Jul 05 2010

LINKS

Table of n, a(n) for n=1..57.

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

FORMULA

a(n) = A042964(n)*2.

a(n) = (4*n - 1 - (-1)^n). - Jon E. Schoenfield, Jul 05 2010

a(n) = 8*n - a(n-1) - 6 (with a(1)=4). - Vincenzo Librandi, Aug 05 2010

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

From Wesley Ivan Hurt, May 18 2013: (Start)

a(n) = (8 * ceiling(n/2) - 4) * (n mod 2) + (8 * ceiling(n/2) - 2) * (n+1 mod 2).

a(n) = 8 * ceiling(n/2) - 3 + (-1)^n. (End)

EXAMPLE

a(2) = 8*2 - 4 - 6 = 6;

a(3) = 8*3 - 6 - 6 = 12;

a(4) = 8*4 - 12 - 6 = 14.

PROG

(PARI) a(n)=4*n-1-(-1)^n \\ Charles R Greathouse IV, May 20 2013

CROSSREFS

Sequence in context: A140599 A282280 A320495 * A136415 A310596 A247456

Adjacent sequences:  A047403 A047404 A047405 * A047407 A047408 A047409

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified April 10 18:17 EDT 2021. Contains 342853 sequences. (Running on oeis4.)