login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A174214 a(n) = a(n-1)+1, if the previous term a(n-1) and n-1-(-1)^n are coprime, else a(n)=2*n-4. 5
14, 16, 17, 18, 19, 20, 26, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 52, 53, 54, 55, 60, 62, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134 (list; graph; refs; listen; history; text; internal format)
OFFSET

9,1

LINKS

Table of n, a(n) for n=9..74.

V. Shevelev, Theorems on twin primes-dual case, arXiv:0912.4006 [math.GM], 2009-2014.

MAPLE

A174214 := proc(n) option remember ; if n = 9 then 14 ; elif gcd(procname(n-1), n-1-(-1)^n) = 1 then procname(n-1)+1 ; else 2*n-4 ; end if; end proc:

seq(A174214(n), n=9..100) ; # R. J. Mathar, Mar 16 2010

MATHEMATICA

a[n_] := a[n] = Which[n==9, 14, CoprimeQ[a[n-1], n-1-(-1)^n], a[n-1]+1, True, 2n-4]; Table[a[n], {n, 9, 100}] (* Jean-Fran├žois Alcover, Feb 02 2016 *)

CROSSREFS

Cf. A166945, A167495.

Sequence in context: A225758 A043663 A043703 * A072709 A241178 A158282

Adjacent sequences:  A174211 A174212 A174213 * A174215 A174216 A174217

KEYWORD

nonn,easy

AUTHOR

Vladimir Shevelev, Mar 12 2010

EXTENSIONS

a(15) corrected and sequence extended by R. J. Mathar, Mar 16 2010

a(15) corrected and a(35)-a(74) added by John W. Layman, Mar 16 2010

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified November 21 12:34 EST 2017. Contains 295001 sequences.