OFFSET
1,2
COMMENTS
Although most small numbers are in the sequence, it becomes sparser for larger values; e.g., only 504 numbers up to 10000 and only 184 numbers from 10001 to 20000 are in the sequence.
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Tau Function.
MATHEMATICA
(* First do <<NumberTheory`Ramanujan` *) test[n_] := Mod[RamanujanTau[n], n]==0; Select[Range[200], test]
(* Second program: *)
Select[Range@ 168, Divisible[RamanujanTau@ #, #] &] (* Michael De Vlieger, Dec 23 2017 *)
PROG
(PARI) for (n=1, 1000, if(Mod(ramanujantau(n), n)==0, print1(n", "))) \\ Dana Jacobsen, Sep 06 2015
(Perl) use ntheory ":all"; my @p = grep { !(ramanujan_tau($_) % $_) } 1..1000; say "@p"; # Dana Jacobsen, Sep 06 2015
(Python)
from itertools import count, islice
from sympy import divisor_sigma
def A063938_gen(startvalue=1): # generator of terms >= startvalue
return filter(lambda n: not -840*(pow(m:=n+1>>1, 2, n)*(0 if n&1 else pow(m*divisor_sigma(m), 2, n))+(sum(pow(i, 4, n)*divisor_sigma(i)*divisor_sigma(n-i) for i in range(1, m))<<1)) % n, count(max(startvalue, 1)))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Robert G. Wilson v, Aug 31 2001
EXTENSIONS
More terms from Dean Hickerson, Jan 03 2003
STATUS
approved