

A242786


Least prime p such that p^n and p^n+1 have the same number of prime factors (counted with multiplicity) or 0 if no such number exists.


2



2, 3, 3, 43, 7, 41, 23, 643, 17, 557, 251, 13183, 1999, 10007, 107
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OFFSET

1,1


COMMENTS

Also least number k > 1 such that k^n and k^n+1 have the same number of prime factors.
Since the data values are prime, p^n and p^n+1 have n prime factors.
a(21) = 1151.


LINKS



EXAMPLE

2^3 = 8 and 2^3 + 1 = 9 do not have the same number of prime factors. 3^3 = 27 and 3^3 + 1 = 28 both have 3 prime factors (27 = 3*3*3 and 28 = 7*2*2). Thus, a(3) = 3.


PROG

(PARI) a(n)=forprime(p=1, oo, if(bigomega(p^n+1)==n, return(p))); \\ Michel Marcus, Sep 21 2018


CROSSREFS



KEYWORD

nonn,more,hard


AUTHOR



EXTENSIONS



STATUS

approved



