A086846 Number of brilliant numbers < 10^n.

3, 10, 73, 241, 2504, 10537, 124363, 573928, 7407840, 35547994, 491316166, 2409600865, 34896253009, 174155363186, 2601913448896, 13163230391312, 201431415980418, 1029540512731472

Offset

1,1

Links

Table of n, a(n) for n=1..18.

Prog

(PARI) a(n) = my(N=10^n-1, count=0, L=#digits(sqrtint(N))); for(k=1, L-1, count += binomial(primepi(10^k) - primepi(10^(k-1)) + 1, 2)); my(min = 10^(L-1), max = 10^L-1, pi_min = primepi(min), pi_max = primepi(max), j = 0); forprime(p = min, max, if(p*p <= N, count += if(N >= p*max, pi_max, primepi(N\p)) - pi_min - j; j+=1, break)); count; \\ Daniel Suteu, Apr 09 2022

Crossrefs

Cf. A078972, A087434, A087435.

Sequence in context: A136507 A334211 A337949 * A277614 A082245 A158033

Adjacent sequences: A086843 A086844 A086845 * A086847 A086848 A086849

Keyword

nonn,more

Author

Jason Earls, Aug 09 2003

Extensions

More terms from Ray Chandler, Aug 31 2003

a(11)-a(14) from Ray Chandler, Jul 21 2005

a(15)-a(16) from Donovan Johnson, May 30 2010

a(17)-a(18) from Daniel Suteu, Apr 09 2022

Status

approved