OFFSET
0,2
LINKS
Henri Lifchitz, Table of n, a(n) for n = 0..23 (first 21 terms from Hiroaki Yamanouchi)
FORMULA
a(n) = A061201(10^n).
PROG
(PARI) a(n)=sum(k=1, 10^n, numdiv(k)*floor((10^n)/k));
vector(7, n, a(n-1)) \\ Altug Alkan, Sep 24 2015
(Python)
from math import isqrt
from sympy import integer_nthroot
def A180365(n): return (m:=integer_nthroot(t:=10**n, 3)[0])**3+3*sum(-(s:=isqrt(r:=t//i))**2+(sum(r//k for k in range(1, s+1))<<1)-sum(t//(i*j) for j in range(1, m+1)) for i in range(1, m+1)) # Chai Wah Wu, Oct 23 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Lelechenko, Jan 19 2011
EXTENSIONS
One more term (a(16)) and typo in crossrefs fixed by Andrew Lelechenko, Apr 13 2011
a(17) from Hiroaki Yamanouchi, Jul 15 2014
STATUS
approved