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Smallest x such that d[phi(x)]-phi[d(x)]=n, where d()=A000005(),phi()=A000010() restricted to cases when d[phi(x)]-phi[d(x)] is positive.
(history; published version)

#6 by N. J. A. Sloane at Tue Oct 15 22:31:44 EDT 2013

AUTHOR

_Labos E. (labos(AT)ana.sote.hu), Elemer_, Nov 26 2002

Discussion

Tue Oct 15

22:31

OEIS Server: https://oeis.org/edit/global/2029

#5 by N. J. A. Sloane at Fri Feb 24 03:00:00 EST 2006

MATHEMATICA

f[x_] := DivisorSigma[0, EulerPhi[x]]-EulerPhi[DivisorSigma[0, x]] t=Table[0, {100}]; Do[s=f[n]; If[s<101&&t[[s]]==0, t[[s]]=n], {n, 1, 100000}]; t

KEYWORD

easy,nonn,new

#4 by N. J. A. Sloane at Tue Jan 24 03:00:00 EST 2006

KEYWORD

easy,nonn,new

AUTHOR

Labos E. (labos(AT)ana1ana.sote.hu), Nov 26 2002

#3 by N. J. A. Sloane at Sat Jun 12 03:00:00 EDT 2004

MATHEMATICA

f[x_] := DivisorSigma[0, EulerPhi[x]]-EulerPhi[DivisorSigma[0, x]] t=Table[0, {100}]; Do[s=f[n]; If[s<101&&t[[s]]==0, t[[s]]=n], {n, 1, 100000}]; t

KEYWORD

easy,nonn,new

#2 by N. J. A. Sloane at Thu Feb 19 03:00:00 EST 2004

MATHEMATICA

f[x_] :=DivisorSigma[0, EulerPhi[x]]-EulerPhi[DivisorSigma[0, x]] t=Table[0, {100}]; Do[s=f[n]; If[s<101&&t[[s]]==0, t[[s]]=n], {n, 1, 100000}]; t

KEYWORD

easy,nonn,new

#1 by N. J. A. Sloane at Fri May 16 03:00:00 EDT 2003

NAME

Smallest x such that d[phi(x)]-phi[d(x)]=n, where d()=A000005(),phi()=A000010() restricted to cases when d[phi(x)]-phi[d(x)] is positive.

DATA

3, 5, 7, 17, 13, 35, 31, 37, 113, 77, 61, 221, 185, 143, 211, 209, 181, 287, 241, 577, 1729, 403, 421, 1297, 1057, 1001, 2113, 779, 1009, 899, 1321, 1917, 5629, 1333, 1801, 2233, 7125, 1763, 2161, 2993, 4433, 4851, 3737, 3311, 51319, 2623, 2521

OFFSET

1,1

MATHEMATICA

f[x_] :=DivisorSigma[0, EulerPhi[x]]-EulerPhi[DivisorSigma[0, x]] t=Table[0, {100}]; Do[s=f[n]; If[s<101&&t[[s]]==0, t[[s]]=n], {n, 1, 100000}]; t

CROSSREFS

Cf. A000005, A000010.

KEYWORD

easy,nonn

AUTHOR

Labos E. (labos(AT)ana1.sote.hu), Nov 26 2002

STATUS

approved