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A377043
The n-th perfect-power A001597(n) minus the n-th power of a prime A000961(n).
2
0, 2, 5, 5, 11, 18, 19, 23, 25, 36, 48, 64, 81, 98, 100, 101, 115, 138, 164, 179, 184, 200, 209, 240, 271, 284, 300, 336, 374, 413, 439, 450, 495, 542, 587, 632, 683, 738, 793, 852, 887, 903, 964, 1029, 1097, 1165, 1194, 1230, 1295, 1370, 1443, 1518, 1561
OFFSET
1,2
COMMENTS
Perfect-powers (A001597) are numbers with a proper integer root.
FORMULA
a(n) = A001597(n) - A000961(n).
MATHEMATICA
perpowQ[n_]:=n==1||GCD@@FactorInteger[n][[All, 2]]>1;
per=Select[Range[1000], perpowQ];
per-NestList[NestWhile[#+1&, #+1, !PrimePowerQ[#]&]&, 1, Length[per]-1]
PROG
(Python)
from sympy import mobius, primepi, integer_nthroot
def A377043(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-1+x+sum(mobius(k)*(integer_nthroot(x, k)[0]-1) for k in range(2, x.bit_length())))
def g(x): return int(n-1+x-sum(primepi(integer_nthroot(x, k)[0]) for k in range(1, x.bit_length())))
return bisection(f, n, n)-bisection(g, n, n) # Chai Wah Wu, Oct 27 2024
CROSSREFS
Excluding 1 from the powers of primes gives A377044.
A000015 gives the least prime-power >= n.
A031218 gives the greatest prime-power <= n.
A000040 lists the primes, differences A001223.
A000961 lists the powers of primes, differences A057820.
A001597 lists the perfect-powers, differences A053289, seconds A376559.
A007916 lists the non-perfect-powers, differences A375706, seconds A376562.
A024619 lists the non-prime-powers, differences A375735, seconds A376599.
A025475 lists numbers that are both a perfect-power and a prime-power.
A080101 counts prime-powers between primes (exclusive).
A106543 lists numbers that are neither a perfect-power nor a prime-power.
A131605 lists perfect-powers that are not prime-powers.
A246655 lists the prime-powers, complement A361102 (differences A375708).
Prime-power runs: A373675, min A373673, max A373674, length A174965.
Prime-power antiruns: A373576, min A120430, max A006549, length A373671.
Sequence in context: A274108 A368616 A138316 * A183719 A239340 A124201
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 25 2024
STATUS
approved