A359644 Number of numbers <= 10^n that are products of 5 distinct primes.

0, 0, 0, 24, 910, 18387, 286758, 3884936, 48396263, 571221133, 6499261245, 72047682376, 783561421371, 8399470576016

Offset

1,4

Links

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

Example

a(4) = 24 = #{2310, 2730, 3570, 3990, 4290, 4830, 5610, 6006, 6090, 6270, 6510, 6630, 7410, 7590, 7770, 7854, 8610, 8778, 8970, 9030, 9282, 9570, 9690, 9870}

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, 5); \\ Daniel Suteu, Jan 10 2023

Crossrefs

Cf. A006880, A036351, A046387, A215218, A359642.

Sequence in context: A006147 A061236 A266997 * A001784 A172206 A220804

Adjacent sequences: A359641 A359642 A359643 * A359645 A359646 A359647

Keyword

nonn,more

Author

Peter Dolland, Jan 09 2023

Extensions

a(14) from Daniel Suteu, Jan 10 2023

Status

approved