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
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
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