A120046 The 10^n-th 5-almost prime.

32, 176, 1272, 10374, 89896, 810220, 7475817

Offset

0,1

Links

Table of n, a(n) for n=0..6.

Mathematica

FiveAlmostPrimePi[n_] := Sum[ PrimePi[n/(Prime@i*Prime@j*Prime@k*Prime@l)] - l + 1, {i, PrimePi[n^(1/5)]}, {j, i, PrimePi[(n/Prime@i)^(1/4)]}, {k, j, PrimePi[(n/(Prime@i*Prime@j)^(1/3))]}, {l, k, PrimePi@Sqrt[(n/(Prime@i*Prime@j*Prime@k))]}];
FiveAlmostPrime[n_] := Block[{e = Floor[Log[2, n] +4], a, b}, a = 2^e; Do[b = 2^p; While[FourAlmostPrimePi[a] < n, a = a + b]; a = a - b/2, {p, e, 0, -1}]; a + b/2]; Do[ Print@FiveAlmostPrime[10^n], {n, 0, 13}]

Crossrefs

Cf. A114453, A006988, A114125, A120044, A120045.

Sequence in context: A181209 A231299 A029534 * A303798 A305243 A304477

Adjacent sequences: A120043 A120044 A120045 * A120047 A120048 A120049

Keyword

hard,more,nonn

Author

Robert G. Wilson v, Feb 15 2006

Status

approved