OFFSET
1,1
COMMENTS
If p>2 and 4*p-1 are prime, then 12*p-4 is in the sequence.
If p>3 and (5*p-1)/2 are prime, then 5*p-2 is in the sequence.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
N:= 20000: # for terms <= N
V:= Vector(N):
for n from 1 to N do
v:= n + numtheory:-phi(n);
if v <= N then V[v]:= V[v]+1 fi
od:
select(t -> V[t]>=2, [$1..N]);
CROSSREFS
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Aug 12 2020
STATUS
approved