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.
a(17) = 5119. - Michel Marcus, Sep 21 2018
a(16) > 10^6; a(18) = 33577; a(19) = 48383. - Jon E. Schoenfield, Sep 22 2018
a(20) > 10^6. - Jon E. Schoenfield, Sep 28 2018
a(16) <= 206874667. - Daniel Suteu, Dec 09 2022
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
Derek Orr, May 22 2014
EXTENSIONS
Data restricted to known terms by Michel Marcus, Sep 21 2018
a(12) & a(14) from Michel Marcus, Sep 21 2018
STATUS
approved