cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A301451 Numbers congruent to {1, 7} mod 9.

Original entry on oeis.org

1, 7, 10, 16, 19, 25, 28, 34, 37, 43, 46, 52, 55, 61, 64, 70, 73, 79, 82, 88, 91, 97, 100, 106, 109, 115, 118, 124, 127, 133, 136, 142, 145, 151, 154, 160, 163, 169, 172, 178, 181, 187, 190, 196, 199, 205, 208, 214, 217, 223, 226, 232, 235, 241, 244, 250, 253, 259, 262, 268
Offset: 1

Views

Author

Bruno Berselli, Mar 21 2018

Keywords

Comments

First bisection of A056991, second bisection of A242660.
The squares of the terms of A174396 are the squares of this sequence.

Crossrefs

Cf. A274406: numbers congruent to {0, 8} mod 9.
Cf. A193910: numbers congruent to {2, 6} mod 9.

Programs

  • GAP
    a := [1,7,10];; for n in [4..60] do a[n] := a[n-1] + a[n-2] - a[n-3]; od; a;
    
  • Magma
    &cat [[9*n+1, 9*n+7]: n in [0..40]];
    
  • Mathematica
    Table[2 (2 n - 1) + (2 n - 3 (1 - (-1)^n))/4, {n, 1, 60}]
    {#+1,#+7}&/@(9*Range[0,30])//Flatten (* or *) LinearRecurrence[{1,1,-1},{1,7,10},60] (* Harvey P. Dale, Nov 08 2020 *)
  • PARI
    Vec(x*(1 + 6*x + 2*x^2) / ((1 - x)^2*(1 + x)) + O(x^60)) \\ Colin Barker, Mar 22 2018
  • Python
    [2*(2*n-1)+(2*n-3*(1-(-1)**n))/4 for n in range(1,70)]
    
  • Sage
    [n for n in (1..300) if n % 9 in (1,7)]
    

Formula

O.g.f.: x*(1 + 6*x + 2*x^2)/((1 + x)*(1 - x)^2).
E.g.f.: (3 + 8*exp(x) - 11*exp(2*x) + 18*x*exp(2*x))*exp(-x)/4.
a(n) = a(n-1) + a(n-2) - a(n-3).
a(n) = 2*(2*n - 1) + (2*n - 3*(1 - (-1)^n))/4. Therefore, for n even a(n) = (9*n - 4)/2, otherwise a(n) = (9*n - 7)/2.
a(2n+1) = A017173(n). a(2n) = A017245(n-1). - R. J. Mathar, Feb 28 2019

A141212 a(n) = 1, if n == {1,3,4} mod 6; otherwise 0.

Original entry on oeis.org

1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1
Offset: 1

Views

Author

Gary W. Adamson, Jun 14 2008

Keywords

Examples

			a(7) = 1 since 7 == 1 mod 6.
		

Crossrefs

Programs

  • Mathematica
    Table[If[MemberQ[{1,3,4},Mod[n,6]],1,0],{n,120}] (* or *) PadRight[{},120,{1,0,1,1,0,0}] (* Harvey P. Dale, May 03 2013 *)

Formula

a(n) = 1 if n is in A029739, otherwise 0.
Begin with the sequence S: (1,0,1,0,1,0,...) and create a hole every 3n-th place: 1,0_1,0_1,0_1,0_,... Then insert terms of the sequence S in the holes.
From R. J. Mathar, Jun 17 2008: (Start)
O.g.f.: x(1+x^2+x^3)/((1-x)(1+x)(x^2+x+1)(x^2-x+1)).
a(n) = 1/2+A049347(n-1)/2-(-1)^n/6-A087204(n)/6 = a(n-6). (End)
a(n) = ((Fibonacci(n+4) mod 4) mod 3) mod 2. - Gary Detlefs, Dec 29 2010
Showing 1-2 of 2 results.