A333874 Numbers k such that A173557(k) = A173557(k+1).

1, 168, 194, 350, 1368, 1628, 3705, 5186, 5328, 6929, 7475, 25545, 26047, 26864, 28251, 34936, 37248, 56724, 65675, 81732, 82368, 87308, 87367, 88450, 91539, 132308, 164691, 166624, 244215, 265524, 280818, 281897, 388245, 465651, 501024, 577524, 806895, 859901

Offset: 1

Author

Amiram Eldar, Apr 08 2020

Keywords

• nonn

Comments

Kim et al. (2019) conjectured that A173557(k) = A173557(k+1) is divisible by 12 for all the terms k > 1.

Examples

			1 is a term since A173557(1) = A173557(2) = 1.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..712 (terms below 2*10^10)
• Daeyeoul Kim, Umit Sarp, and Sebahattin Ikikardes, Certain combinatoric convolution sums arising from Bernoulli and Euler Polynomials, Miskolc Mathematical Notes, No. 20, Vol. 1 (2019): pp. 311-330.

Crossrefs

Cf. A001274, A173557, A333875.

Programs

Mathematica

f[p_, e_] := p - 1; u[1] = 1; u[n_] := Times @@ (f @@@ FactorInteger[n]); s = {}; u1 = 1; Do[u2 = u[n]; If[u1 == u2, AppendTo[s, n-1]]; u1 = u2, {n, 2, 10^5}]; s