A174612 Number of four-prime Carmichael numbers less than 10^n.

0, 0, 0, 0, 0, 4, 19, 55, 144, 314, 619, 1179, 2102, 3639, 6042, 9938, 16202, 25758, 40685, 63343, 98253, 151566, 232742, 357078, 548265

Offset

0,6

References

Paulo Ribenboim, The Little Book of Bigger Primes, Springer-Verlag, NY, 2004. See p. 220.

Links

Table of n, a(n) for n=0..24.

Claude Goutier, Text file readme.text summarizing enumeration of Carmichael numbers up to 10^22.

Claude Goutier, Text file readme.text summarizing enumeration of Carmichael numbers up to 10^22. [Local copy, with permission]

R. G. E. Pinch, The Carmichael numbers up to 10^21, Proceedings of Conference on Algorithmic Number Theory 2007.

Andrew Shallue and Jonathan Webster, Algorithms for Carmichael numbers, arXiv:2506.09903 [math.NT], 2025-2026.

Index entries for sequences related to Carmichael numbers.

Example

For n=5, the smallest Carmichael number with 4 prime factors is 41041 = 7*11*13*41.

Crossrefs

For k-prime Carmichael numbers up to 10^n for k = 3,4,...,11, see A132195, A174612, A174613, A174614, A174615, A174616, A174617, A299710, A299711.

Cf. A002997, A006931, A055553.

Sequence in context: A122684 A122681 A215862 * A020496 A108484 A283333

Adjacent sequences: A174609 A174610 A174611 * A174613 A174614 A174615

Keyword

nonn,more

Author

Michel Lagneau, Mar 23 2010

Extensions

a(0) inserted and a(22) from Claude Goutier added by Amiram Eldar, Apr 19 2024

a(23)-a(24) from Shallue and Webster (2025-2026) added by Amiram Eldar, Jan 24 2026

Status

approved