A087434 Number of brilliant numbers whose prime factors each have n digits.

10, 231, 10296, 563391, 34974066, 2374052871, 171745762321, 12989075028126, 1016377282340160, 81690831917887753, 6708792934060150753, 560785267822390134615, 47573053155260626453431

Offset: 1

Author

Ray Chandler, Sep 02 2003

Keywords

• nonn
• base

Comments

Number of brilliant numbers having 2n or 2n-1 digits.

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..24

Crossrefs

Cf. A006879, A006880, A078972, A086846, A087435.

Programs

PARI

a(n)=binomial(primepi(10^n)-primepi(10^(n-1))+1,2)
\\ Charles R Greathouse IV, May 03 2012

Formula

a(n)=A000217(A006879(n)).

Extensions

a(14) from Ray Chandler, Jul 21 2005