A207575 -id:A207575 - cp's OEIS frontend

A207574 Numbers k such that phi(k)+2 divides k+2.

1, 6, 10, 14, 22, 26, 34, 38, 46, 58, 62, 74, 82, 86, 94, 106, 118, 122, 134, 142, 146, 158, 166, 178, 194, 202, 206, 214, 218, 226, 254, 262, 274, 278, 298, 302, 314, 326, 334, 346, 358, 362, 382, 386, 390, 394, 398, 422, 446, 454, 458, 466, 478

Offset: 1

José María Grau Ribas, Feb 19 2012

Consists of the even semiprimes (other than 4) together with A207575. - Charles R Greathouse IV, Jul 15 2013

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A000010, A207575, A202855, A203966.

Select[Range[1000],Divisible[#+2,EulerPhi[#]+2]&]

isA207574(n)={
        if( (n+2) % (eulerphi(n)+2) ==0,1,0) ;
}
{
for(n=1,200,
        if (isA207574(n) , print(n)) ;
) ;
} /* R. J. Mathar, Feb 23 2012 */

A226105 Numbers k such that phi(k)+3 divides k+3, excluding numbers of the form 6*p for a prime p.

Original entry on oeis.org

1, 195, 5187, 1141967133868035, 3658018932844533311864835

Offset: 1

José María Grau Ribas, May 26 2013

Terms having (k+3)/(phi(k)+3) = 2 are shared with A350777. - Max Alekseyev, Oct 26 2023

Set difference of A226104 and 6 * A000040.

Cf. A202855, A203966, A207575, A207667, A350777.

Select[Range[10000000], !PrimeQ[#/6] && IntegerQ[(# + 3)/(EulerPhi[#] + 3)] &]

for(n=1,10^8, if( (n+3)%(eulerphi(n)+3)==0 && (n%6 || !isprime(n\6)), print(n)));

Edited and a(4)-a(5) added by Max Alekseyev, Nov 05 2023

cp's OEIS Frontend

A207574 Numbers k such that phi(k)+2 divides k+2.

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