A051832 Numbers k such that (2*10^(5*k) - 10^(4*k) + 2*10^(3*k) + 10^(2*k) + 10^k + 1)/3 is prime.

0, 1, 7, 133

Offset: 1

Author

G. L. Honaker, Jr., Dec 11 1999

Keywords

• hard
• nonn

Comments

The Baxter-Hickerson function provides a number whose cube lacks zeros.

The next term is > 4400. - Jason Earls, Sep 10 2005

The next term is > 20000 (found using pfgw64). - Patrick De Geest, Jul 22 2012

Links

• Ed Pegg, Jr., Fun with numbers.
• Eric Weisstein's World of Mathematics, Baxter-Hickerson Function.

Crossrefs

Cubes: A052044, A052045, A051750, A051751, A051833. Squares: A052040, A052041, A052042, A052043.

Programs

Maple

f := n->(2*10^(5*n) - 10^(4*n) + 2*10^(3*n) + 10^(2*n) + 10^n + 1)/3;

PARI

is(n)=isprime((2*10^(5*n)-10^(4*n)+2*10^(3*n)+10^(2*n)+10^n+1)/3) \\ Charles R Greathouse IV, Feb 17 2017