A333408 Numbers k such that s(k) = s(k+1), where s(k) is the unitary analog of the alternating sum-of-divisors function (A307037).

1, 11, 71, 155, 194, 204, 1119, 1420, 1628, 3705, 5186, 14363, 19788, 20467, 25180, 25545, 25843, 28251, 30804, 42811, 60204, 63180, 71791, 73260, 83600, 87219, 87308, 91539, 97432, 99208, 100456, 100471, 119315, 122616, 132308, 135340, 135864, 164691, 166624

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..1000

Example

1 is a term since s(1) = s(2) = 1;
11 is a term since s(11) = s(12) = 10;

Mathematica

f[p_, e_] := p^e + (-1)^e; s[1] = 1; s[n_] := Times @@ f @@@ FactorInteger[n]; seq = {}; s1 = 1;  Do[s2 = s[n]; If[s1 == s2, AppendTo[seq, n - 1]]; s1 = s2, {n, 2, 10^5}]; seq

Crossrefs

The unitary version of A206368.

Cf. A206369, A307037.

Sequence in context: A255205 A117047 A089720 * A174202 A139850 A233416

Adjacent sequences: A333405 A333406 A333407 * A333409 A333410 A333411

Keyword

nonn

Author

Amiram Eldar, Mar 19 2020

Status

approved