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A184390
a(n) = sum of numbers from 1 to pi(n), where pi(n) = A007955(n).
5
1, 3, 6, 36, 15, 666, 28, 2080, 378, 5050, 66, 1493856, 91, 19306, 25425, 524800, 153, 17009028, 190, 32004000, 97461, 117370, 276, 55037822976, 7875, 228826, 266085, 240956128, 435, 328050405000
OFFSET
1,2
LINKS
FORMULA
a(n) = Sum_{i = 1..pi(n)} i = A000217(A007955(n)) = (1/2)*A007955(n)*(A007955(n)+1).
EXAMPLE
For n = 6; pi(6) = 36; a(n) = (1/2)*36*37 = 666.
MATHEMATICA
# (#+1)/2&/@Array[Times@@Divisors[#]&, 40] (* Harvey P. Dale, Oct 05 2012 *)
PROG
(Python)
from math import isqrt
from sympy import divisor_count
def A184390(n): return (m:=((isqrt(n) if (c:=divisor_count(n)) & 1 else 1)*n**(c//2)))*(m+1)//2 # Chai Wah Wu, Jun 25 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Jan 12 2011
STATUS
approved