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!)
A169598 Numbers that are congruent to {3,18} mod 23. 1
3, 18, 26, 41, 49, 64, 72, 87, 95, 110, 118, 133, 141, 156, 164, 179, 187, 202, 210, 225, 233, 248, 256, 271, 279, 294, 302, 317, 325, 340, 348, 363, 371, 386, 394, 409, 417, 432, 440, 455, 463, 478, 486, 501, 509, 524, 532, 547, 555, 570, 578, 593, 601, 616, 624 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Conjecture: For no n in the sequence 36*n^2+72*n+35 = (6*n+5)*(6*n+7) is of the form p*(p+2), where p and p+2 are primes.

The conjecture is evident, it can be proved as in A169599. [Bruno Berselli, Jan 07 2013]

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

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

FORMULA

a(n) = (46*n + 7*(-1)^n - 27)/4. - Vincenzo Librandi, Jan 06 2013, modified Jul 07 2015

a(n) = a(n-1) + a(n-2) - a(n-3). - Vincenzo Librandi, Jan 06 2013

G.f.: x*(3+15*x+5*x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Jul 07 2015

MAPLE

A169598:=n->(46*n + 7*(-1)^n - 27)/4: seq(A169598(n), n=1..100); # Wesley Ivan Hurt, Feb 05 2017

MATHEMATICA

Select[Range[624], MemberQ[{3, 18}, Mod[#, 23]]&] (* Ray Chandler, Jul 08 2015 *)

LinearRecurrence[{1, 1, -1}, {3, 18, 26}, 55] (* Ray Chandler, Jul 08 2015 *)

Rest[CoefficientList[Series[x*(3+15*x+5*x^2)/((1+x)*(x-1)^2), {x, 0, 55}], x]] (* Ray Chandler, Jul 08 2015 *)

CROSSREFS

Cf. A169599.

Sequence in context: A263578 A048080 A306279 * A202359 A118474 A163242

Adjacent sequences:  A169595 A169596 A169597 * A169599 A169600 A169601

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Dec 03 2009

EXTENSIONS

Added leading terms. Clarified comment. - R. J. Mathar, Jul 07 2015

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 January 28 10:02 EST 2020. Contains 331319 sequences. (Running on oeis4.)