A217773 Numbers n such that tau(n) = tau(n+1) and phi(n) = phi(n+1).

104, 3255, 22935, 983775, 1025504, 2200694, 2619705, 4163355, 4447064, 4695704, 6372794, 9718904, 11903775, 23992215, 26879684, 29357475, 37239735, 40588485, 41207144, 48615735, 56424555, 76466985, 81591194, 83864055, 113664135, 118018094, 166758015

Offset: 1

Author

Jayanta Basu, Mar 24 2013

Keywords

• nonn

Comments

Intersection of A001274 and A005237. [Alex Ratushnyak, Mar 27 2013]

Links

• Donovan Johnson, Table of n, a(n) for n = 1..402 (terms < 10^12)

Crossrefs

Cf. A001274, A005237.

Programs

Mathematica

Select[Range[100000000],DivisorSigma[0, #] == DivisorSigma[0, # + 1] && EulerPhi[#] == EulerPhi[# + 1] &]
Position[Partition[Table[{DivisorSigma[0,n],EulerPhi[n]},{n,1668*10^5}], 2,1], ?(#[[1]]==#[[2]]&),1,Heads->False]//Flatten (* _Harvey P. Dale, Nov 20 2019 *)