A331000 Unitary Ruth-Aaron numbers: numbers k such that A008475(k) = A008475(k+1).

5, 77, 714, 948, 2491, 2996, 3450, 4293, 5405, 6669, 9125, 10807, 13869, 14587, 16932, 17346, 19511, 19967, 23323, 26642, 27104, 31931, 33019, 37925, 41124, 43616, 48635, 52554, 55499, 58077, 58695, 79248, 80837, 86088, 89979, 95709, 98644, 99163, 108458, 117467

Offset

1,1

Comments

A variation of Ruth-Aaron numbers with unitary prime-power divisors instead of prime divisors.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

5 is a term since A008475(5) = A008475(6) = 5.

Mathematica

s[1] = 0; s[n_] := Plus @@ (Power @@@ FactorInteger[n]); seq = {}; s1 = 0; Do[s2 = s[n]; If[s1 == s2, AppendTo[seq, n - 1]]; s1 = s2, {n, 2, 10^5}]; seq

Crossrefs

Cf. A006145, A039752, A008475, A330999.

Sequence in context: A364713 A214867 A330999 * A039753 A277533 A186662

Adjacent sequences: A330997 A330998 A330999 * A331001 A331002 A331003

Keyword

nonn

Author

Amiram Eldar, Jan 05 2020

Status

approved