A231816 a(n) = the smallest squarefree number (A005117) with n prime factors in a 2p-1 progression.

2, 6, 30, 351137972965951, 8596208716179446431, 698211042943963834650959743951, 744014385572130806167897354113929551, 901203402294977554329263775346819632824908852456695769189267773301

Offset

1,1

Comments

Smallest squarefree numbers with n >= 2 prime divisors of the form p_1 * p_2 * … * p_n, where p_1 < p_2 < … < p_k = primes with p_k = 2 * p_(k-1) - 1.

Subsequence of A231814.

Links

Jaroslav Krizek, Table of n, a(n) for n = 1..15

Example

8596208716179446431 = 1531*3061*6121*12241*24481, where 3061 = 2*1531 - 1, 6121 = 2*3061 - 1, 12241 = 2*6121 - 1, 24481 = 2*12241 - 1.

Crossrefs

Cf. A005117, A000040, A231814, A231815.

Cf. A057330 (first prime for such numbers that has n factors).

Sequence in context: A153046 A088260 A232171 * A058028 A216834 A287592

Adjacent sequences: A231813 A231814 A231815 * A231817 A231818 A231819

Keyword

nonn

Author

Jaroslav Krizek, Nov 13 2013

Status

approved