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A145748 Numbers n such that phi(n+1)-phi(n)=sigma(n+1)-sigma(n). 2
2, 854, 751358, 1421637, 8775206, 8892195, 16485944, 31845344, 95494035, 277653495, 380438505, 744048855, 1091725394, 1615353002, 2284844925, 2491028745, 6345217034, 8490513014, 12784909335, 14177454885, 15669084375, 17694356295, 17836667354, 24180347115 (list; graph; refs; listen; history; text; internal format)
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.

Sequence in context: A028485 A034227 A324589 * A141185 A257660 A128667

Adjacent sequences:  A145745 A145746 A145747 * A145749 A145750 A145751

KEYWORD

nonn

AUTHOR

Farideh Firoozbakht, Nov 01 2008

EXTENSIONS

a(9)-a(16) from Donovan Johnson, Dec 14 2009

a(17)-a(24) from Donovan Johnson, Feb 08 2012

STATUS

approved

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Last modified October 26 06:08 EDT 2021. Contains 348257 sequences. (Running on oeis4.)