A047405 Numbers that are congruent to {0, 1, 2, 3, 6} mod 8.

0, 1, 2, 3, 6, 8, 9, 10, 11, 14, 16, 17, 18, 19, 22, 24, 25, 26, 27, 30, 32, 33, 34, 35, 38, 40, 41, 42, 43, 46, 48, 49, 50, 51, 54, 56, 57, 58, 59, 62, 64, 65, 66, 67, 70, 72, 73, 74, 75, 78, 80, 81, 82, 83, 86, 88, 89

Offset

1,3

Comments

For n >= 2, 5*(a(n)+k)*Pi; where k = 0, 4, 3, 1 if n mod 5 = 0 or 1, 2, 3, 4 respectively; is also the total length of irregular spiral (center points: 1, 4, 3, 2, 5) after (n-1) rotations. - Kival Ngaokrajang, Jan 08 2014

Links

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

Kival Ngaokrajang, Illustration of irregular spiral (center points: 1, 4, 3, 2, 5)

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

Formula

G.f.: x^2*(2*x^2 - x + 1)*(1+x)^2 / ( (x^4 + x^3 + x^2 + x + 1)*(x-1)^2 ). - R. J. Mathar, Dec 05 2011

a(n) ~ 8*n/5. - Charles R Greathouse IV, Jun 02 2026

Prog

(PARI) a(n)=(n-1)\5*8+[6, 0, 1, 2, 3][n%5+1] \\ Charles R Greathouse IV, Jun 02 2026

Crossrefs

Sequence in context: A139371 A335962 A079338 * A175904 A084090 A353988

Adjacent sequences: A047402 A047403 A047404 * A047406 A047407 A047408

Keyword

nonn,easy,changed

Author

N. J. A. Sloane

Status

approved