OFFSET
1,3
LINKS
Peter Kagey, Table of n, a(n) for n = 1..1000
EXAMPLE
a(1) = 1;
a(2) = 1 because a(1) has at most as many divisors as 2;
a(3) = 3 because a(1) and a(2) have at most as many divisors as 3;
a(4) = 6 because a(1), a(2), and a(3) have at most as many divisors as 4;
a(5) = 6 because a(1), a(2), and a(3) have at most as many divisors as 5.
MATHEMATICA
a = {1}; Do[d = DivisorSigma[0, n]; AppendTo[a, Total@ Select[Range[n - 1], DivisorSigma[0, a[[#]]] <= d &]], {n, 2, 54}]; a (* Michael De Vlieger, Mar 24 2016 *)
PROG
(Java)
int[] terms = new int[100];
terms[0] = 1;
for (int i = 1; i < 100; i++) {
int count = 0;
for (int j = 0; j < i; j++) {
if (divisors(terms[j]) <= divisors(i+1)) {
count = count + j + 1;
}
}
terms[i] = count;
}
(PARI) lista(nn) = {va = vector(nn); print1(va[1] = 1, ", "); for (n=2, nn, va[n] = sum(k=1, n-1, k*(numdiv(va[k]) <= numdiv(n))); print1(va[n], ", "); ); } \\ Michel Marcus, Feb 29 2016
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Alec Jones, Feb 29 2016
STATUS
approved