A241793 Least number k such that k^n and k^n-1 contain the same number of prime factors (counted with multiplicity) or 0 if no such k exists.

3, 34, 5, 15, 17, 55, 79, 5, 53, 23, 337, 13, 601, 79, 241, 41, 18433, 31, 40961, 89, 3313, 1153

Offset

1,1

Comments

a(23) > 3250.

a(24) = 79. - Jacques Tramu, Sep 16 2018

100000 < a(23) <= 286721. - Jon E. Schoenfield, Sep 25 2018

Links

Table of n, a(n) for n=1..22.

Example

2^1 (2) and 2^1-1 (1) do not have the same number of prime factors. 3^1 (3) and 3^1-1 (2) have the same number of prime factors. Thus a(1) = 3.

Prog

(PARI) a(n)=for(k=2, oo, if(bigomega(k^n)==bigomega(k^n-1), return(k)));

Crossrefs

Cf. A001222 (bigomega), A242786.

Sequence in context: A134477 A080985 A006854 * A225427 A037103 A197220

Adjacent sequences: A241790 A241791 A241792 * A241794 A241795 A241796

Keyword

nonn,more,hard

Author

Derek Orr, May 23 2014

Extensions

a(17) and a(19) corrected by Jacques Tramu, Sep 16 2018

Status

approved