1
$\begingroup$

I want to check sum of divisors of i mod 13 fori = 1 to i = 20. I tried writing a Do-Print loop so it looks like

Do[Print[DivisorSigma[1, i], {i, 20} mod 13] 

Any help will be greatly appreciated,

$\endgroup$
2
$\begingroup$
Table[DivisorSigma[1, i], {i, 20} ] // Mod[#, 13] &
(*{1, 3, 4, 7, 6, 12, 8, 2, 0, 5, 12, 2, 1, 11, 11, 5, 5, 0, 7, 3}*)

or

Do[Print[Mod[DivisorSigma[1, i], 13]], {i, 20}]

which gives a column of the same numbers as before that you can look at, but it is more difficult use in further expressions.

$\endgroup$
  • $\begingroup$ thank you so much $\endgroup$ – argamon Feb 19 at 22:28
  • $\begingroup$ You're welcome. $\endgroup$ – Bill Watts Feb 19 at 22:29
2
$\begingroup$

You can do it without iterators because the functions you need (Mod, DivisorSigma) are Listable:

Mod[DivisorSigma[1, Range[20]], 13]

{1, 3, 4, 7, 6, 12, 8, 2, 0, 5, 12, 2, 1, 11, 11, 5, 5, 0, 7, 3}

Note: Listable functions are applied separately to each element in a list.

$\endgroup$
  • $\begingroup$ that's also very useful and helpful thank you $\endgroup$ – argamon Feb 19 at 22:56

Not the answer you're looking for? Browse other questions tagged or ask your own question.