A073797 - OEIS

A073797

a(n) = 2^n mod pi(n).

0, 0, 0, 2, 1, 0, 0, 0, 0, 3, 1, 2, 4, 2, 4, 4, 1, 0, 0, 0, 0, 5, 1, 2, 4, 8, 7, 2, 4, 2, 4, 8, 5, 10, 9, 8, 4, 8, 4, 6, 12, 2, 4, 8, 2, 8, 1, 2, 4, 8, 1, 0, 0, 0, 0, 0, 0, 8, 16, 2, 4, 8, 16, 14, 10, 3, 6, 12, 5, 8, 16, 2, 4, 8, 16, 11, 1, 6, 12, 2, 4, 18, 13, 3, 6, 12, 1, 8, 16, 8, 16, 8, 16, 8, 16

(list; graph; refs; listen; history; text; internal format)

OFFSET

2,4

LINKS

Michael De Vlieger, Table of n, a(n) for n = 2..10000

FORMULA

a(n) = A000079(n) mod A000720(n).

EXAMPLE

From Michael De Vlieger, Dec 09 2018: (Start)

a(2) = 0 since 2^2 mod PrimePi(2) = 4 mod 1 = 0.

a(5) = 2 since 2^5 mod PrimePi(5) = 32 mod 3 = 2. (End)

MATHEMATICA

Array[Mod[2^#, PrimePi@ #] &, 95, 2] (* Michael De Vlieger, Dec 09 2018 *)

Table[PowerMod[2, n, PrimePi[n]], {n, 2, 100}] (* Harvey P. Dale, Aug 30 2021 *)

PROG

(PARI) for(n=2, 100, print1(lift(Mod(2^n, primepi(n))), ", ")) \\ G. C. Greubel, Dec 10 2018

(Magma) [2^n mod #PrimesUpTo(n): n in [2..100]]; // G. C. Greubel, Dec 10 2018

(Sage) [mod(2^n, prime_pi(n)) for n in (2..100)] # G. C. Greubel, Dec 10 2018

CROSSREFS

Cf. A000079, A000720, A015910, A062173, A064367.

Sequence in context: A368821 A250002 A035195 * A037856 A037874 A343870

Adjacent sequences: A073794 A073795 A073796 * A073798 A073799 A073800

KEYWORD

nonn

AUTHOR

Labos Elemer, Aug 12 2002

STATUS

approved