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A192221
Numbers n such that phi(n-2)=phi(n+2) where phi=A000010.
1
10, 16, 18, 22, 37, 54, 66, 93, 142, 150, 246, 294, 405, 457, 618, 630, 774, 803, 1013, 1026, 1110, 1146, 1254, 1272, 1297, 1458, 1590, 1686, 1822, 1830, 2032, 2166, 2454, 2625, 2646, 2662, 2694, 2934, 3030, 3218, 3323, 3510, 3990, 4266, 4342, 4374, 4614, 4806, 4854, 4950, 5182, 5286
OFFSET
1,1
FORMULA
a(n) = A179186(n)+2. - R. J. Mathar, Jun 26 2011
MATHEMATICA
Select[Range[3, 5000], EulerPhi[# - 2] == EulerPhi[# + 2] &] (* Alonso del Arte, Jun 28 2011 *)
Flatten[Position[Partition[EulerPhi[Range[5300]], 5, 1], _?(#[[1]] == #[[5]]&), 1, Heads -> False]]+2 (* Harvey P. Dale, Jul 01 2019 *)
PROG
(PARI) for(n=3, 1e4, if(eulerphi(n-2)==eulerphi(n+2), print1(n", "))) \\ Charles R Greathouse IV, Jun 27 2011
CROSSREFS
Sequence in context: A352240 A187797 A352297 * A106695 A053747 A228491
KEYWORD
nonn
AUTHOR
STATUS
approved