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 A167768 First of 4 or more consecutive integers with equal values of phi(phi(n)). 2
 1, 7, 31, 32, 2694, 131071, 50802031105 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Next term > 1266046940 (last term of A167767 b-file). - Michel Marcus, Jun 23 2013 No other terms < 1.32*10^12. - Jud McCranie, Jul 19 2017 LINKS EXAMPLE p2(1) = p2(2) = p2(3) = p2(4) = 1, p2(7) = p2(8) = p2(9) = p2(10) = 2. MATHEMATICA a[n_] := EulerPhi[EulerPhi[n]]; Select[Range[10000], a[#] == a[# + 1] && a[# + 1] == a[# + 2] && a[# + 2] == a[# + 3] &] (* G. C. Greubel, Jun 23 2016 *) PROG (PARI) pp(n) = eulerphi(eulerphi(n)) isA167768(n) = pp(n)==pp(n+1) && pp(n+1)==pp(n+2) && pp(n+2)==pp(n+3) \\ Michael B. Porter, Nov 24 2009 CROSSREFS Cf. A167767 (of which this list is a subset), A167766. Sequence in context: A065916 A122654 A184121 * A103630 A205711 A040064 Adjacent sequences:  A167765 A167766 A167767 * A167769 A167770 A167771 KEYWORD more,nonn,hard AUTHOR Fred Schneider, Nov 11 2009 EXTENSIONS Edited by N. J. A. Sloane, Nov 12 2009 a(7) added by Jud McCranie, Jul 17 2017 STATUS approved

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Last modified June 5 16:19 EDT 2020. Contains 334852 sequences. (Running on oeis4.)