login
This site is supported by donations to The OEIS Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A245515 a(n) = n*floor(mod((gcd(n, Fibonacci((-1)^n + n))), 1 + n)/n) for n>=2. 1
1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 11, 0, 0, 0, 0, 0, 0, 0, 19, 0, 0, 0, 0, 0, 0, 0, 0, 0, 29, 0, 31, 0, 0, 0, 0, 0, 0, 0, 0, 0, 41, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 59, 0, 61, 0, 0, 0, 0, 0, 0, 0, 0, 0, 71, 0, 0, 0, 0, 0, 0, 0, 79, 0, 0, 0, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Sequence with many prime numbers and zeros.

The primes occurring in this sequence are given in A064739. The subsequence of composite numbers starts 1891, 2737, 2834, 4181, 6601, 6721, 8149, 13201, 13981, ... - Joerg Arndt, Nov 19 2017

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

José de Jesús Camacho Medina, Table with 140 first nonzero terms of this sequence (Una interesante fórmula generadora de 140 primos).

FORMULA

a(n) = n*floor(mod((gcd(n, fibonacci((-1)^n + n))), 1 + n)/n) for n>=1.

EXAMPLE

For n=1, a(1)=1; for n=2, a(2)=2.

MAPLE

f:= n -> n*floor(modp((igcd(n, combinat:-fibonacci((-1)^n + n))), 1 + n)/n):

seq(f(n), n=1..100); # Robert Israel, Jul 25 2014

MATHEMATICA

Table[n*Floor[Mod[(GCD[n, Fibonacci[(-1)^n + n]]), 1 + n]/n], {n, 1, 1890}]

PROG

(PARI) a(n) = n*((gcd(n, fibonacci((-1)^n + n)) % (1 + n))\n); \\ Michel Marcus, Jul 25 2014

(PARI) a(n)=gcd(n, lift(((Mod([1, 1; 1, 0], n))^(n+(-1)^n))[1, 2]))\n*n \\ Charles R Greathouse IV, Jul 25 2014

(MAGMA) [n*((Gcd(n, Fibonacci((-1)^n+n)) mod (1+n)) div n): n in [1..100]]; // Vincenzo Librandi, Dec 17 2016

CROSSREFS

Sequence in context: A114099 A028613 A318381 * A024362 A104488 A244413

Adjacent sequences:  A245512 A245513 A245514 * A245516 A245517 A245518

KEYWORD

nonn

AUTHOR

José de Jesús Camacho Medina, Jul 24 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 January 17 22:51 EST 2019. Contains 319251 sequences. (Running on oeis4.)