OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
45 is in the sequence because 45-phi(45) = 21, which is an octagonal number.
MATHEMATICA
octQ[n_] := n == 0 || IntegerQ[(Sqrt[48*n + 16] + 4)/12]; Select[Range[250], octQ[# - EulerPhi[#]] &] (* Amiram Eldar, Mar 23 2021 *)
PROG
(PARI) isok(n) = ispolygonal(n - eulerphi(n), 8); \\ Michel Marcus, Feb 26 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 23 2006
EXTENSIONS
Offset corrected by Amiram Eldar, Mar 23 2021
STATUS
approved