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

1,1

Comments

The number of prime factors is always >= 3.

Links

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

Formula

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

Prog

(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

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).

Sequence in context: A303168 A162844 A115787 * A259581 A105592 A210745

Adjacent sequences: A300956 A300957 A300958 * A300960 A300961 A300962

Keyword

nonn

Author

Tim Johannes Ohrtmann, Mar 17 2018

Status

approved