A336464 Numbers k for which A335915(k), A335915(sigma(k)) and A335915(sigma(sigma(k))) obtain the same value.

1, 2, 28, 56, 60, 84, 160, 168, 528, 12936, 32760, 102960, 1097280, 1778400, 11740302, 19183500, 25241600, 235855620, 308308000, 317167200, 424305000, 459818240, 704700000, 787200000, 924924000, 1592025435, 2701416960, 3812244480

Offset

1,2

Comments

Numbers k for which A335915(k) = A336455(k) = A336456(k).

Numbers k such that both k and sigma(k) are in A336461.

Note that a(26) = 1592025435 (originally found by David A. Corneth) is an odd term > 1, which factorizes as 3^5 * 7^2 * 11^2 * 5 * 13 * 17, and thus is not of the form of A228058.

It appears that if we instead list k such that both k and sigma(k) are in A336458, we will not obtain more than these three terms: 1, 2, 84.

Links

Table of n, a(n) for n=1..28.

Index entries for sequences where odd perfect numbers must occur, if they exist at all

Crossrefs

Cf. A000203, A000265, A228058, A335915, A336455, A336456, A336458, A336560.

Intersection of any two of these three sequences: A336461, A336462, A336463.

Sequence in context: A177829 A363875 A339990 * A245801 A296245 A156471

Adjacent sequences: A336461 A336462 A336463 * A336465 A336466 A336467

Keyword

nonn,more

Author

Antti Karttunen, Jul 22 2020

Status

approved