A076529 Numbers k for which phi(k) = phi(k+1) - phi(k-1).

2, 4, 6, 10, 16, 22, 36, 40, 46, 100, 136, 232, 256, 856, 1036, 1296, 1540, 1600, 2016, 4336, 6526, 9178, 14400, 16096, 30496, 55386, 61132, 62800, 65536, 72580, 77616, 110176, 152650, 179296, 244966, 299650, 603460, 619696, 686736, 1876726, 2841916, 3058210

Offset: 1

Author

Joseph L. Pe, Oct 18 2002

Keywords

• nonn

Examples

			phi(22) = 10; phi(23) = 22; phi(21) = 12 and 10 = 22 - 12; hence 22 is a term of the sequence.
		

Links

• Donovan Johnson, Table of n, a(n) for n = 1..100

Crossrefs

Cf. A000010, A220160.

Programs

Mathematica

Select[Range[2, 10^5], EulerPhi[#] == EulerPhi[#+1] - EulerPhi[#-1] &]
Flatten[ Position[Partition[EulerPhi[Range[31*10^5]],3,1],?(#[[2]] == #[[3]] -#[[1]]&),1,Heads->False]]+1 (* _Harvey P. Dale, Dec 28 2017 *)

Extensions

Missing first term added by Donovan Johnson, Dec 06 2012