A290592 Numbers x such that x = Sum_{j=1..k} d(j*x), for some k, where d(x) is the number of divisors of x.

1, 2, 9, 10, 26, 34, 46, 76, 121, 128, 136, 140, 174, 194, 226, 230, 232, 240, 268, 278, 296, 325, 362, 370, 432, 434, 438, 575, 598, 610, 620, 637, 694, 708, 718, 734, 735, 756, 796, 808, 842, 854, 860, 866, 898, 922, 925, 986, 1048, 1050, 1072, 1168, 1196, 1228

Offset

1,2

Comments

Values of k for the listed items are 1, 1, 2, 2, 4, 5, 6, 7, 14, 9, 9, 7, 11, 19, 21, 13, 14, 8, 19, 25, 17, 18, 31, 19, 13, 21, 23, 29, 27, 28, 22, 31, 53, 26, 54, 55, 23, 17, 45, 38, 62, 36, 29, 63, 65, 66, 42, 40, 47, 21, 41, 44, 36, 65.

All squarefree terms > 1 are even. - Robert Israel, Aug 07 2017

Links

Robert Israel, Table of n, a(n) for n = 1..1000

Example

For 34 we have that d(34) + d(2*34) + d(3*34) + d(4*34) + d(5*34) = 4 + 6 + 8 + 8 + 8 = 34.

Maple

with(numtheory): P:=proc(n) local a, k; a:=0; k:=0; while a<n do k:=k+1;
a:=a+tau(k*n); od; if a=n then n; fi; end: seq(P(i), i=1..2000);

Crossrefs

Cf. A000005, A270713, A270389.

Sequence in context: A191576 A081346 A301872 * A058551 A119183 A179888

Adjacent sequences: A290589 A290590 A290591 * A290593 A290594 A290595

Keyword

nonn,easy

Author

Paolo P. Lava, Aug 07 2017

Status

approved