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

1,1

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

Formula

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

Prog

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

Crossrefs

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

Sequence in context: A349731 A239772 A239773 * A297648 A012240 A295410

Adjacent sequences: A087431 A087432 A087433 * A087435 A087436 A087437

Keyword

nonn,base

Author

Ray Chandler, Sep 02 2003

Extensions

a(14) from Ray Chandler, Jul 21 2005

Status

approved