A048123 Smallest n-digit Carmichael numbers.

561, 1105, 10585, 101101, 1024651, 10024561, 100427041, 1001152801, 10017089857, 100023777217, 1000151515441, 10000879761601, 100000782192961, 1000040508690301, 10000092861302401, 100001371359120001, 1000004296444433281, 10000011591390633121

Offset: 3

Author

Shyam Sunder Gupta, Feb 17 2002

Keywords

• hard
• more
• nonn
• base

Examples

			a(4)=1105 because 1105 is the smallest 4-digit Carmichael number. [corrected by _Jon E. Schoenfield_, Jan 28 2014]
		

Crossrefs

Cf. A062568, A062852, A063400.

Programs

Mathematica

CarmichaelNbrQ[n_] := ! PrimeQ@ n && Mod[n, CarmichaelLambda@ n] == 1; f[n_] := Block[{k = 10^(n - 1) + 1}, While[! CarmichaelNbrQ@ k, k += 2]; k]; Do[ Print[{n, f[n] // Timing}], {n, 3, 18}]

Extensions

a(17)-a(20) from Amiram Eldar, Jun 29 2019