A300959 Number of prime factors of the n-th Lucas-Carmichael number.

3, 3, 3, 3, 3, 3, 3, 4, 3, 4, 3, 3, 3, 4, 4, 3, 4, 3, 3, 3, 4, 3, 3, 4, 3, 3, 3, 4, 3, 4, 3, 3, 4, 4, 4, 3, 3, 4, 3, 4, 4, 3, 4, 3, 5, 4, 3, 3, 3, 3, 4, 3, 3, 4, 3, 4, 4, 3, 3, 3, 5, 4, 4, 3, 3, 4, 3, 4, 3, 3, 4, 4, 4, 3, 3, 4, 4, 3, 4, 4, 4, 4, 3, 5, 3, 4, 3

Offset: 1

Author

Tim Johannes Ohrtmann, Mar 17 2018

Keywords

• nonn

Comments

The number of prime factors is always >= 3.

Links

• Tim Johannes Ohrtmann, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A006972 (Lucas-Carmichael numbers).

Cf. A216925, A216926, A216927, A217002, A217003, A217091 (Lucas-Carmichael numbers with 3 to 8 prime factors).

Cf. A216928 (Least Lucas-Carmichael number with n prime factors).

Programs

PARI

islc(n)=my(f=factor(n)); for(i=1, #f[, 1], if((n+1)%(f[i, 1]+1) || f[i, 2]>1, return(0))); #f[, 1]>1; \\ from A006972
lista(nn) = for (n=1, nn, if (islc(n), print1(omega(n), ", "))); \\ Michel Marcus, Mar 17 2018

Formula

a(n) = A001221(A006972(n)).