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URL: https://oeis.org/A230006

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A230006
Numbers k such that sigma(k) + phi(k) = reversal(k) + 1.
5
1, 37, 225, 397, 11112722, 1309286244182
OFFSET
1,2
COMMENTS
If p = 4*10^m-3 is prime then p is in the sequence.
a(7) > 10^13. - Giovanni Resta, Feb 08 2014
EXAMPLE
sigma(37)+phi(37) = 38+36 = 73+1 = reversal(37)+1.
MATHEMATICA
r[n_] := FromDigits[Reverse[IntegerDigits[n]]]; Do[If[DivisorSigma[1, n] + EulerPhi[n] == r[n]+1, Print[n]], {n, 1000000000}]
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Farideh Firoozbakht, Dec 02 2013
EXTENSIONS
a(6) from Giovanni Resta, Feb 06 2014
STATUS
approved