OFFSET
1,1
COMMENTS
A000244 is a subset of this sequence.
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..73 (terms < 2*10^12)
EXAMPLE
27*28/2 mod sigma(27) = 378 mod 40 = 18 = phi(27).
MAPLE
with(numtheory): P:=proc(q) local n;
for n from 1 to q do if (n*(n+1)/2) mod sigma(n)=phi(n) then print(n); fi;
od; end: P(10^6);
MATHEMATICA
Select[Range[10^5], Function[n, Mod[Total@ First@ #, Total@ Last@ #] == EulerPhi@ n &@ {Complement[Range@ n, #], #} &@ Divisors@ n]] (* Michael De Vlieger, Apr 27 2016 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paolo P. Lava, Apr 26 2016
EXTENSIONS
a(27)-a(34) from Giovanni Resta, May 01 2016
STATUS
approved