A073456 Numbers n such that phi(n) = pi(n)+1.

1, 5, 36, 48, 84

Offset

1,2

Links

Table of n, a(n) for n=1..5.

Formula

Solutions to A000010(x)=A000720(x)+k, where k=+1; finite for any fixed value of k.

Example

15 primes below 48 = {2,3,5,7,11,13,17,19,23,29,31,37,41,43,47}; 16 terms in RRS[48]={1,5,7,11,13,17,19,23,25,29,31,35,37,41,43,47}, so 48 is here.

Mathematica

Do[s=EulerPhi[n]-PrimePi[n]; If[Equal[s, 1], Print[n]], {n, 1, 10000}]
Select[Range[100], EulerPhi[#]==PrimePi[#]+1&] (* Harvey P. Dale, Oct 23 2024 *)

Crossrefs

Cf. A037228, A037171, A000010, A000720, A073455.

Sequence in context: A263882 A035416 A042029 * A275223 A003350 A344643

Adjacent sequences: A073453 A073454 A073455 * A073457 A073458 A073459

Keyword

fini,full,nonn

Author

Labos Elemer, Aug 02 2002

Extensions

Definition modified by Harvey P. Dale, Oct 23 2024

Status

approved