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%I #11 Apr 15 2020 12:31:28
%S 7,635,1015,2695,6497,10307,12317,13445,46205,77693,81303,133787,
%T 134995,151823,162925,180633,181427,220113,288925,359905,392819,
%U 404471,439097,453167,485237,682649,739023,840851,879303,910195,988713,1392317,1410119,1434895,1503347
%N Odd numbers k such that phi(k) = phi(k+2), where phi is the Euler totient function (A000010).
%C The odd terms of A001494. These terms are relatively rare: of the first 10000 terms of A001494 only 63 are odd.
%H Amiram Eldar, <a href="/A333741/b333741.txt">Table of n, a(n) for n = 1..1000</a>
%e 7 is a term since phi(7) = phi(9) = 6.
%t Select[Range[1, 10^6, 2], EulerPhi[#] == EulerPhi[# + 2] &]
%t 2#-1&/@SequencePosition[EulerPhi[Range[1,151*10^4,2]],{x_,x_}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Apr 15 2020 *)
%Y Cf. A000010, A001274.
%K nonn
%O 1,1
%A _Amiram Eldar_, Apr 03 2020
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