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%I #13 Jan 12 2023 15:09:21
%S 0,0,0,24,910,18387,286758,3884936,48396263,571221133,6499261245,
%T 72047682376,783561421371,8399470576016
%N Number of numbers <= 10^n that are products of 5 distinct primes.
%e 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}
%o (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
%Y Cf. A006880, A036351, A046387, A215218, A359642.
%K nonn,more
%O 1,4
%A _Peter Dolland_, Jan 09 2023
%E a(14) from _Daniel Suteu_, Jan 10 2023
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