The On-Line Encyclopedia of Integer Sequences (OEIS)

The OEIS is supported by the many generous donors to the OEIS Foundation.

Revision History for A157419

(Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing all changes.

A157419

a(0)=1. a(n) = the smallest integer coprime to a(n-1) and greater than the n-th prime.
(history; published version)

#10 by N. J. A. Sloane at Mon Oct 30 22:39:47 EDT 2017

STATUS

proposed

approved

#9 by Michael De Vlieger at Mon Oct 30 22:12:48 EDT 2017

STATUS

editing

proposed

#8 by Michael De Vlieger at Mon Oct 30 22:12:44 EDT 2017

LINKS

Michael De Vlieger, <a href="/A157419/b157419.txt">Table of n, a(n) for n = 0..10000</a>

MATHEMATICA

Fold[Append[#1, Block[{k = Prime@ #2 + 1}, While[! CoprimeQ[k, #1[[-1]] ], k++]; k]] &, {1}, Range@ 59] (* Michael De Vlieger, Oct 30 2017 *)

STATUS

approved

editing

#7 by Charles R Greathouse IV at Tue Mar 11 01:32:28 EDT 2014

AUTHOR

__Leroy Quet__, , Feb 28 2009

Discussion

Tue Mar 11

01:32

OEIS Server: https://oeis.org/edit/global/2122

#6 by N. J. A. Sloane at Wed Feb 05 20:18:57 EST 2014

AUTHOR

__Leroy Quet_, _, Feb 28 2009

Discussion

Wed Feb 05

20:18

OEIS Server: https://oeis.org/edit/global/2118

#5 by N. J. A. Sloane at Wed Feb 05 20:12:01 EST 2014

AUTHOR

_Leroy Quet, _, Feb 28 2009

Discussion

Wed Feb 05

20:12

OEIS Server: https://oeis.org/edit/global/2117

#4 by Russ Cox at Fri Mar 30 17:29:59 EDT 2012

EXTENSIONS

Extended by _Ray Chandler (rayjchandler(AT)sbcglobal.net), _, Jun 19 2009

Discussion

Fri Mar 30

17:29

OEIS Server: https://oeis.org/edit/global/154

#3 by N. J. A. Sloane at Sat Oct 02 03:00:00 EDT 2010

KEYWORD

nonn,new

nonn

AUTHOR

Leroy Quet (http://www.prism-of-spirals.net/), , Feb 28 2009

#2 by N. J. A. Sloane at Sun Jul 11 03:00:00 EDT 2010

KEYWORD

nonn,new

nonn

AUTHOR

Leroy Quet (q1qq2qqq3qqqq(AT)yahoohttp://www.prism-of-spirals.comnet/), Feb 28 2009

#1 by N. J. A. Sloane at Tue Jun 01 03:00:00 EDT 2010

NAME

a(0)=1. a(n) = the smallest integer coprime to a(n-1) and greater than the n-th prime.

DATA

1, 3, 4, 7, 8, 13, 14, 19, 20, 27, 31, 32, 39, 43, 44, 49, 54, 61, 62, 69, 73, 74, 81, 85, 91, 99, 103, 104, 109, 110, 117, 128, 133, 138, 143, 150, 157, 158, 165, 169, 174, 181, 182, 193, 194, 199, 200, 213, 224, 229, 230, 237, 241, 242, 255, 259, 264, 271, 272, 279

OFFSET

0,2

EXAMPLE

a(8) = 20, and the 9th prime is 23. So for a(9) we want the smallest integer that is both coprime to 20 and is > 23. Checking: 24 is not coprime to 20. 25 is not coprime to 20. 26 is not coprime to 20. But 27 is coprime to 20, so a(9) = 27.

CROSSREFS

Cf. A157420, A157421.

KEYWORD

nonn

AUTHOR

Leroy Quet (q1qq2qqq3qqqq(AT)yahoo.com), Feb 28 2009

EXTENSIONS

Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jun 19 2009

STATUS

approved