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!)
A027626 Denominator of n*(n+5)/((n+2)*(n+3)). 3
1, 2, 10, 5, 7, 28, 12, 15, 55, 22, 26, 91, 35, 40, 136, 51, 57, 190, 70, 77, 253, 92, 100, 325, 117, 126, 406, 145, 155, 496, 176, 187, 595, 210, 222, 703, 247, 260, 820, 287, 301, 946, 330, 345, 1081, 376, 392, 1225, 425, 442, 1378, 477, 495, 1540, 532, 551 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Or numerator of (n+2)*(n+3)/6. - Altug Alkan, Apr 18 2018

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (0,0,3,0,0,-3,0,0,1).

FORMULA

a(n) = GCD of n-th and (n+1)st tetrahedral numbers (A000292). - Ross La Haye, Sep 13 2003

G.f.: (x^8-2x^5+x^4+2x^3+10x^2+2x+1)/(1-x^3)^3.

a(n) = A234041(n+1) = A107711(n+4,3) = C(n+3,2)*gcd(n+4,3)/3 for n >= 0. See the o.g.f. of A234041. - Wolfdieter Lang, Feb 26 2014

MATHEMATICA

CoefficientList[Series[(x^8 - 2 x^5 + x^4 + 2 x^3 + 10 x^2 + 2 x + 1)/(1 - x^3)^3, {x, 0, 50}], x] (* Vincenzo Librandi, Mar 04 2014 *)

PROG

(MAGMA) [Denominator(n*(n+5) / ((n+2)*(n+3))): n in [0..60]]; // Vincenzo Librandi, Mar 04 2014

(PARI) a(n) = numerator((n+2)*(n+3)/6); \\ Altug Alkan, Apr 18 2018

CROSSREFS

Cf. A027625, A107711, A234041.

Sequence in context: A213603 A145911 A234041 * A096668 A114232 A070730

Adjacent sequences:  A027623 A027624 A027625 * A027627 A027628 A027629

KEYWORD

nonn,frac,easy

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Vincenzo Librandi, Mar 04 2014

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 June 13 18:45 EDT 2021. Contains 345008 sequences. (Running on oeis4.)