A359645 Number of numbers <= 10^n that are products of 6 distinct primes.

0, 0, 0, 0, 20, 1235, 32396, 605939, 9446284, 131733664, 1706815354, 21008871506, 249145286508, 2873325692759

Offset

1,5

Links

Table of n, a(n) for n=1..14.

Example

a(5) = 20 = #{30030, 39270, 43890, 46410, 51870, 53130, 62790, 66990, 67830, 71610, 72930, 79170, 81510, 82110, 84630, 85470, 91770, 94710, 98670, 99330}.

Prog

(PARI) a(n) = my(N=10^n); (f(m, p, k, j=1)=my(s=sqrtnint(N\m, k), count=0); if(k==2, forprime(q=p, s, count += primepi(N\(m*q)) - j; j+=1); return(count)); forprime(q=p, s, count += f(m*q, q+1, k-1, j+1); j+=1); count); f(1, 2, 6); \\ Daniel Suteu, Jan 11 2023

Crossrefs

Cf. A006880, A036351, A067885, A215218, A359642, A359644.

Sequence in context: A158912 A036067 A294191 * A001451 A093598 A174581

Adjacent sequences: A359642 A359643 A359644 * A359646 A359647 A359648

Keyword

nonn,more

Author

Peter Dolland, Jan 09 2023

Extensions

a(13)-a(14) from Daniel Suteu, Jan 11 2023

Status

approved