A145748 - OEIS

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A145748

Numbers n such that phi(n+1)-phi(n)=sigma(n+1)-sigma(n).

2, 854, 751358, 1421637, 8775206, 8892195, 16485944, 31845344, 95494035, 277653495, 380438505, 744048855, 1091725394, 1615353002, 2284844925, 2491028745, 6345217034, 8490513014, 12784909335, 14177454885, 15669084375, 17694356295, 17836667354, 24180347115

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OFFSET

1,1

COMMENTS

This sequence is a subsequence of A066198.

LINKS

Table of n, a(n) for n=1..24.

MATHEMATICA

de[n_]:=DivisorSigma[1, n]-EulerPhi[n]; Do[If[de[n]==de[n+1], Print[n]], {n, 50000000}] (* Firoozbakht *)

Select[Range[10^6], (EulerPhi[# + 1] - EulerPhi[#]) == (DivisorSigma[1, # + 1] - DivisorSigma[1, #]) &] (* Alonso del Arte, Feb 08 2012 *)

CROSSREFS

Cf. A066198, A145749.