A375593 Index i among the divisors of k = A375574(n) of the sum s of the first n divisors of k.
1, 3, 4, 5, 6, 8, 10, 10, 11, 19, 20, 16, 20, 28, 22, 32, 29, 29, 29, 27, 38, 40, 39, 47, 33, 42, 52, 55, 43, 46, 36, 47, 45, 47, 54, 58, 70, 51, 59, 62, 60, 77, 48, 80, 82, 75, 67, 79, 67, 68, 80, 84, 91, 62, 107, 98, 99, 88, 112, 103, 120, 70, 96, 88, 89, 72, 98
Offset: 1
Keywords
Examples
a(24) = 47 because the sum of the 24 first divisors of k = A375574(24) = 11088 is s = 1+2+3+4+6+7+8+9+11+12+14+16+18+21+22+24+28+33+36+42+44+48+56+63 = 528 which is the 47th divisor of 11088.
Crossrefs
Cf. A375574.
Programs
-
Maple
with(numtheory):nn:=10^7:T:=array(1..79):i:=0: for n from 2 to 80 do: ii:=1: for a from 6 to nn while ii=1 do: d:=divisors(a):n0:=nops(d): if n0>=n then s:=sum('d[j]', 'j'=1..n): for m from 1 to n0 do: if s=d[m] then ii:=0:printf(`%d %d %d\n`,n,a,m):i:=i+1:T[i]:=m: else fi : od :fi: od:od:print(T): -
Python
from sympy import divisors from itertools import count, islice def agen(): # generator of terms adict, n = dict(), 1 for k in count(1): d = divisors(k) if len(d) < n-1: continue dset, s = set(d), 0 for i, di in enumerate(d, 1): s += di if i >= n and i not in adict and s in dset: adict[i] = d.index(s) + 1 while n in adict: yield adict[n]; n += 1 print(list(islice(agen(), 65))) # Michael S. Branicky, Aug 20 2024
Comments