OFFSET
1,1
COMMENTS
a(n) tends to sqrt(2)*(10^n) when n->oo.
MATHEMATICA
a[n_] := Floor[Sqrt[EulerPhi[10^n] * DivisorSigma[1, 10^n] + 100^n]]; Array[a, 20] (* Amiram Eldar, Jun 12 2022 *)
PROG
(PARI) a(n) = my(w=10^n); sqrtint(eulerphi(w)*sigma(w)+w^2); \\ Michel Marcus, Mar 23 2020
(Python)
from sympy import integer_nthroot, totient as phi, divisor_sigma as sigma
def isqrt(n): return integer_nthroot(n, 2)[0]
def a(n): w = 10**n; return isqrt(phi(w)*sigma(w, 1) + w**2)
print([a(n) for n in range(1, 21)]) # Michael S. Branicky, Jun 12 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 13 2001
EXTENSIONS
Corrected and extended by Michel Marcus, Jun 12 2022
STATUS
approved