OFFSET
1,1
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
EXAMPLE
78125=5^7 follows 78121
MATHEMATICA
Take[NextPrime[#, -1]&/@Union[Flatten[Table[Prime[p]^n, {n, 2, 20}, {p, 25}]]], 50] (* Harvey P. Dale, Mar 26 2012 *)
PROG
(PARI) { m=1; for (n=1, 1000, m++; while(sigma(m)*eulerphi(m)*(1 - isprime(m)) <= (m - 1)^2, m++); write("b060845.txt", n, " ", precprime(m - 1)); ) } \\ Harry J. Smith, Jul 19 2009
(Python)
from sympy import primepi, integer_nthroot, prevprime
def A060845(n):
def bisection(f, kmin=0, kmax=1):
while f(kmax) > kmax: kmax <<= 1
while kmax-kmin > 1:
kmid = kmax+kmin>>1
if f(kmid) <= kmid:
kmax = kmid
else:
kmin = kmid
return kmax
def f(x): return int(n+x-sum(primepi(integer_nthroot(x, k)[0]) for k in range(2, x.bit_length())))
return prevprime(bisection(f, n, n)) # Chai Wah Wu, Sep 15 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, May 03 2001
STATUS
approved