OFFSET
1,4
COMMENTS
This sequence hits every positive integer and each term repeats at most three times.
FORMULA
MATHEMATICA
Nest[Append[#1, #1[[EulerPhi@ #2]] + #1[[#2 - EulerPhi@ #2]] ] & @@ {#, Length@ #} &, {1, 1, 1}, 88] (* Michael De Vlieger, Jul 01 2018 *)
PROG
(PARI) q=vector(99); for(n=1, 3, q[n] = 1); for(n=4, #q, q[n] = q[eulerphi(n)] + q[n-eulerphi(n)]); q
(GAP) a:=[1, 1, 1];; for n in [4..80] do a[n]:=a[Phi(n)]+a[n-Phi(n)]; od; a; # Muniru A Asiru, Jul 01 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Altug Alkan, Jul 01 2018
STATUS
approved