login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A047345 Numbers that are congruent to {0, 4} mod 7. 14
0, 4, 7, 11, 14, 18, 21, 25, 28, 32, 35, 39, 42, 46, 49, 53, 56, 60, 63, 67, 70, 74, 77, 81, 84, 88, 91, 95, 98, 102, 105, 109, 112, 116, 119, 123, 126, 130, 133, 137, 140, 144, 147, 151, 154, 158, 161, 165, 168, 172, 175, 179, 182, 186, 189, 193 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Nonnegative k such that k or 5*k + 1 is divisible by 7. - Bruno Berselli, Feb 13 2018

Maximum number of 2's possible in an infinite Minesweeper grid with n mines. The pattern of mines (x) that generates these 2's looks like "...xx.xx.xx...". - Dmitry Kamenetsky, Apr 14 2018

LINKS

Table of n, a(n) for n=1..56.

Wikipedia, Minesweeper.

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

FORMULA

a(n) = ceiling(7*(n-1)/2).

a(n) = 7*n - a(n-1) - 10 for n>1, a(1)=0. - Vincenzo Librandi, Aug 05 2010

From R. J. Mathar, Oct 08 2011: (Start)

a(n) = 7*n/2 - 13/4 + (-1)^n/4.

G.f.: x^2*(4 + 3*x) / ((1 + x)*(x - 1)^2). (End)

a(n+1) = Sum_{k>=0} A030308(n,k)*b(k), with b(0) = 4, b(k) = A005009(k-1) = 7*2^(k-1), and k>0. - Philippe Deléham, Oct 17 2011.

a(n) = 4*(n - 1) - floor((n - 1)/2). - Wesley Ivan Hurt, Jun 14 2013

a(n) = 2*(n - 1) + floor((3*n - 2 - (n mod 2))/2). - Wesley Ivan Hurt, Mar 31 2014

MAPLE

A047345:=n->ceil(7*(n-1)/2); seq(A047345(n), n=1..100); # Wesley Ivan Hurt, Mar 31 2014

MATHEMATICA

Table[Ceiling[7 (n - 1)/2], {n, 100}] (* Wesley Ivan Hurt, Mar 31 2014 *)

PROG

(PARI) forstep(n=0, 200, [4, 3], print1(n", ")) \\ Charles R Greathouse IV, Oct 17 2011

CROSSREFS

Cf. A030123.

Sequence in context: A190769 A083051 A198269 * A310728 A247157 A087070

Adjacent sequences:  A047342 A047343 A047344 * A047346 A047347 A047348

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 17 20:44 EDT 2021. Contains 343990 sequences. (Running on oeis4.)