login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A244438 Terms of the sequence A145749 which are not of the form 2*p where p is prime. 2
8, 188, 285, 902, 2013, 8493, 37406, 40977, 61918, 68210, 90094, 303853, 352941, 360446, 375565, 467654, 501693, 724934, 889285, 940093, 1079662, 1473565, 1488957, 1517206, 1573045, 1692302, 1864285, 2048973, 2077405, 2346226, 2584106, 2693517, 3393934, 3509997, 3802029, 4083526, 4194406 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 1..702

MATHEMATICA

Select[Range[5000000], !PrimeQ[#/2] && DivisorSigma[1, #] + EulerPhi[#] == DivisorSigma[1, # + 1] + EulerPhi[# + 1] &]

PROG

(PARI)

for(n=1, 10^7, s=eulerphi(n)+sigma(n); if(s==eulerphi(n+1)+sigma(n+1) && ((n%2==0 && !isprime(n/2)) || n%2), print1(n, ", "))) \\ Derek Orr, Aug 14 2014

CROSSREFS

Cf. A000010, A000203, A005384, A145749.

Sequence in context: A198153 A197233 A163701 * A272529 A198282 A177147

Adjacent sequences:  A244435 A244436 A244437 * A244439 A244440 A244441

KEYWORD

nonn

AUTHOR

Farideh Firoozbakht, Aug 14 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 20 10:43 EDT 2021. Contains 348100 sequences. (Running on oeis4.)