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.

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A377032 Odd numbers k such that A000045(k)/A000005(k) is an integer.

Original entry on oeis.org

1, 3, 405, 625, 1875, 50625, 354375, 556875, 658125, 860625, 961875, 1164375, 1468125, 1500625, 1569375, 1873125, 2075625, 2176875, 2379375, 2683125, 2986875, 3088125, 3391875, 3594375, 3695625, 3720087, 3999375, 4201875, 4501875, 4505625, 4910625, 5113125, 5214375, 5416875, 5518125, 5720625
Offset: 1

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Author

Robert Israel, Oct 14 2024

Keywords

Comments

Odd numbers k such that Fibonacci(k) is divisible by tau(k).
Includes 15^4 * p for primes p > 5.

Examples

			a(3) = 405 is a term because 405 = 3^4 * 5 is odd, tau(405) = 10, and Fibonacci(405) = 1952132532477489958194625524584538730388053593825001030592563956919572392152809678530 is divisible by 10.
		

Crossrefs

Intersection of A160684 and A005408.

Programs

  • Maple
    filter:= proc(n) uses LinearAlgebra:-Modular; local t, Mt,dt;
      t:= numtheory:-tau(n);
      if t < 2^25 then Mt:= Mod(t, M, float[8]) else Mt:= Mod(t, M, integer) fi;;
      MatrixPower(t,M,n)[1,2] = 0
    end proc:
    filter(1):= true:
    select(filter, [seq(i,i=1..600000,2)]);
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