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.

A047485 Numbers that are congruent to {0, 3, 5, 7} mod 8.

Original entry on oeis.org

0, 3, 5, 7, 8, 11, 13, 15, 16, 19, 21, 23, 24, 27, 29, 31, 32, 35, 37, 39, 40, 43, 45, 47, 48, 51, 53, 55, 56, 59, 61, 63, 64, 67, 69, 71, 72, 75, 77, 79, 80, 83, 85, 87, 88, 91, 93, 95, 96, 99, 101, 103, 104, 107, 109, 111, 112, 115, 117, 119, 120, 123, 125
Offset: 1

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Formula

From Colin Barker, May 14 2012: (Start)
G.f.: x^2*(3+2*x+2*x^2+x^3)/((1-x)^2*(1+x)*(1+x^2)).
a(n) = (-5+(-1)^n-i*(-i)^n+i*i^n+8*n)/4 where i=sqrt(-1). (End)
From Wesley Ivan Hurt, Jun 04 2016: (Start)
a(n) = a(n-1) + a(n-4) - a(n-5) for n>5.
a(2k) = A004767(k-1) for n>0, a(2k-1) = A047615(k). (End)
E.g.f.: (2 - sin(x) + (4*x - 3)*sinh(x) + (4*x - 2)*cosh(x))/2. - Ilya Gutkovskiy, Jun 04 2016
Sum_{n>=2} (-1)^n/a(n) = (8-sqrt(2))*log(2)/16 + sqrt(2)*log(2+sqrt(2))/8 - (3-sqrt(2))*Pi/16. - Amiram Eldar, Dec 23 2021