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A217773 Numbers n such that tau(n) = tau(n+1) and phi(n) = phi(n+1). 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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)

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 *)

CROSSREFS

Cf. A001274, A005237.

Sequence in context: A281536 A250684 A299601 * A298460 A299553 A187530

Adjacent sequences:  A217770 A217771 A217772 * A217774 A217775 A217776

KEYWORD

nonn

AUTHOR

Jayanta Basu, Mar 24 2013

STATUS

approved

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Last modified November 29 14:23 EST 2020. Contains 338769 sequences. (Running on oeis4.)