OFFSET
0,2
COMMENTS
Cumulative sum of A007503, starting with 1.
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 0..10000
PROG
(PARI) alist(n)=my(x); vector(n, k, if(k==1, x=1, x+=sigma(k-1)+numdiv(k-1)))
(Haskell)
a257644 n = a257644_list !! n
a257644_list = scanl (+) 1 a007503_list -- Reinhard Zumkeller, Nov 09 2015
(Python)
from math import isqrt
def A257644(n): return (-(s:=isqrt(n))*(s*(s+4)+5)+sum(((q:=n//w)+1)*(q+(w<<1)+4) for w in range(1, s+1))>>1)+1 # Chai Wah Wu, Oct 31 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Franklin T. Adams-Watters, Nov 05 2015
STATUS
approved