A257644 First differences of A264100.

1, 3, 8, 14, 24, 32, 48, 58, 77, 93, 115, 129, 163, 179, 207, 235, 271, 291, 336, 358, 406, 442, 482, 508, 576, 610, 656, 700, 762, 794, 874, 908, 977, 1029, 1087, 1139, 1239, 1279, 1343, 1403, 1501, 1545, 1649, 1695, 1785, 1869, 1945, 1995, 2129, 2189

Offset: 0

Author

Franklin T. Adams-Watters, Nov 05 2015

Keywords

• nonn

Comments

Cumulative sum of A007503, starting with 1.

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A000005, A000203, A007503, A264100.

Programs

Haskell

a257644 n = a257644_list !! n
a257644_list = scanl (+) 1 a007503_list -- Reinhard Zumkeller, Nov 09 2015

PARI

alist(n)=my(x);vector(n,k,if(k==1,x=1,x+=sigma(k-1)+numdiv(k-1)))

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