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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A237521 Numbers n such that phi(n) + sigma(n) = reversal(n) + 2. 4
 2, 22605, 26026, 492775589 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(5), if it exists, is larger than 10^13. Up to 10^13 the equation phi(n) + sigma(n) = reversal(n) - 2 is satisfied only by n = 26330276. LINKS EXAMPLE 22605 is in the sequence because phi(22605) = 10880, sigma(22605) = 39744, and 10880 + 39744 = 50622 + 2, where 50622 is the reversal of 22605. MATHEMATICA Select[Range[493*10^6], EulerPhi[#]+DivisorSigma[1, #]== IntegerReverse[ #]+2&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 01 2020 *) CROSSREFS Cf. A070272, A230004, A230005, A230006, A230019, A136544, A237522. Sequence in context: A290741 A261362 A132942 * A131558 A133857 A232869 Adjacent sequences:  A237518 A237519 A237520 * A237522 A237523 A237524 KEYWORD nonn,base,more AUTHOR Giovanni Resta, Feb 08 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.

Last modified January 26 20:11 EST 2020. Contains 331288 sequences. (Running on oeis4.)