

A269525


a(1) = 1, a(n) is the sum of m < n for which a(m) has at most as many divisors as n.


1



1, 1, 3, 6, 6, 15, 6, 28, 6, 37, 16, 66, 16, 47, 61, 100, 45, 125, 45, 162, 94, 115, 45, 240, 45, 137, 163, 306, 98, 347, 128, 365, 252, 252, 252, 456, 128, 252, 252, 477, 128, 558, 128, 437, 481, 341, 128, 819, 128, 572, 387, 623, 128, 988
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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, n1, k*(numdiv(va[k]) <= numdiv(n))); print1(va[n], ", "); ); } \\ Michel Marcus, Feb 29 2016


CROSSREFS

Sequence in context: A119306 A107972 A238775 * A036252 A103463 A265026
Adjacent sequences: A269522 A269523 A269524 * A269526 A269527 A269528


KEYWORD

easy,nonn


AUTHOR

Alec Jones, Feb 29 2016


STATUS

approved



