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A067198
Numbers n such that sigma(n) = phi(n) + phi(n-1).
0
5, 7, 77, 6293, 12943, 23495, 30191, 99695, 147407, 240425, 258401, 535601, 1103825, 1570145, 1637867, 1972607, 2219135, 2241281, 2970517, 3785951, 5612321, 5917003, 6215951, 9249241, 9281899, 12496429, 14779531, 25739701, 30367321, 33522251, 33852841
OFFSET
1,1
EXAMPLE
sigma(5) = 6 = 4 + 2 = phi(5) + phi(5-1), so 5 is a term of the sequence.
MATHEMATICA
Select[Range[2, 10^5], EulerPhi[ # ] + EulerPhi[ # - 1] == DivisorSigma[1, # ] &]
CROSSREFS
Sequence in context: A098967 A107140 A141746 * A340468 A351636 A062583
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Feb 19 2002
EXTENSIONS
a(9)-a(31) from Donovan Johnson, Mar 01 2012
STATUS
approved