A298761 Numbers n such that n = pi(n) + uphi(n), where pi = A000720, uphi = A047994.

2, 20, 35, 40, 44, 215, 235, 245, 2611, 23319, 26288, 65113, 174647, 318544, 1301317, 1302509, 1919376, 3719225, 5021647, 10885081, 36319939, 49172608, 70112131, 70113559, 325575773, 514258883, 742327529, 1069238453

Offset

1,1

Comments

The unitary version of A037170.

Links

Table of n, a(n) for n=1..28.

Example

20 is in the sequence since pi(20) + uphi(20) = 8 + 12 = 20.

Mathematica

uphi[n_] := (Times @@ (Table[#[[1]]^#[[2]] - 1, {1}] & /@ FactorInteger[n]))[[1]]; seqQ[n_] := (n - uphi[n] == PrimePi[n]); Select[Range[10^7], seqQ]

Prog

(PARI) uphi(n) = my(f=factor(n)); prod(k=1, #f~, f[k, 1]^f[k, 2]-1);
isok(n) = n == primepi(n) + uphi(n); \\ Michel Marcus, Feb 13 2018

Crossrefs

Cf. A000720, A037170, A047994.

Sequence in context: A201122 A103076 A293029 * A062133 A329729 A050684

Adjacent sequences: A298758 A298759 A298760 * A298762 A298763 A298764

Keyword

nonn,more

Author

Amiram Eldar, Jan 26 2018

Extensions

a(20)-a(22) from Daniel Suteu, Mar 28 2018

a(23)-a(28) from Daniel Suteu, Nov 18 2018

Status

approved