A318272 a(n) is the least k such that A049417(A049417(k)) = n*k, where A049417 is the infinitary sigma function, or 0 if no such k exists.

1, 2, 8, 15, 24, 60, 1321920, 17850, 285600, 763776

Offset

1,2

Comments

It is also known that a(12) = 71400.

Then for higher indices n, we have:

a(11) <= 414230544000;

a(13) <= 2667897127526400;

a(14) <= 446464417259520;

a(15) <= 23613006957281280;

a(16) <= 22227004800;

a(17) <= 3134896756992000;

a(18) <= 15414516736819200;

a(20) <= 53129265653882880.

a(16) = 8420630400. - Giovanni Resta, Aug 25 2018

Links

Table of n, a(n) for n=1..10.

Tomohiro Yamada, Infinitary superperfect numbers, Annales Mathematicae et Informaticae, 47 (2017) pp. 211-218. See Table 1.

Crossrefs

Cf. A049417, A318182.

Cf. A272930 (analog for sigma), A318242 (analog for bi-unitary sigma).

Sequence in context: A063286 A133230 A318242 * A244476 A292202 A189952

Adjacent sequences: A318269 A318270 A318271 * A318273 A318274 A318275

Keyword

nonn,more

Author

Michel Marcus, Aug 23 2018

Status

approved