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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A300288 Irregular triangle read by rows: row n contains numbers k such that -n<=k<=n and gcd(k, 2*n+1) != 1. 1

%I

%S 0,0,0,-3,0,3,0,0,-6,-5,-3,0,3,5,6,0,0,-9,-7,-6,-3,0,3,6,7,9,0,-10,-5,

%T 0,5,10,-12,-9,-6,-3,0,3,6,9,12,0,0,-15,-12,-11,-9,-6,-3,0,3,6,9,11,

%U 12,15,-15,-14,-10,-7,-5,0,5,7,10,14,15,0,-18,-15,-13,-12,-9,-6,-3,0,3,6,9,12,13,15,18,0

%N Irregular triangle read by rows: row n contains numbers k such that -n<=k<=n and gcd(k, 2*n+1) != 1.

%C Row n contains 2*n+1 - phi(2*n+1) = A053193(n) terms. Row n has just one term (namely 0) if 2*n+1 is prime.

%F T(n,k) = A299714(n,k) - n.

%e Triangle starts:

%e [01]: 0,

%e [02]: 0,

%e [03]: 0,

%e [04]: -3, 0, 3,

%e [05]: 0,

%e [06]: 0,

%e [07]: -6, -5, -3, 0, 3, 5, 6,

%e [08]: 0,

%e [09]: 0,

%e [10]: -9, -7, -6, -3, 0, 3, 6, 7, 9,

%e [11]: 0,

%e [12]: -10, -5, 0, 5, 10,

%e [13]: -12, -9, -6, -3, 0, 3, 6, 9, 12,

%e [14]: 0,

%e [15]: 0,

%e [16]: -15, -12, -11, -9, -6, -3, 0, 3, 6, 9, 11, 12, 15,

%e [17]: -15, -14, -10, -7, -5, 0, 5, 7, 10, 14, 15,

%e [18]: 0,

%e [19]: -18, -15, -13, -12, -9, -6, -3, 0, 3, 6, 9, 12, 13, 15, 18,

%e [20]: 0,

%e ...

%o (PARI) is(n, k)= ( gcd(k, 2*n+1)!=1 );

%o for (n=1, 33, for (k=-n, +n, if (is(n, k), print1(k, ", ") ); ); );

%Y Cf. A299714.

%K sign,tabf

%O 1,4

%A _Joerg Arndt_, Mar 02 2018

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

Last modified March 25 07:42 EDT 2023. Contains 361511 sequences. (Running on oeis4.)