A063710 - OEIS

A063710

Numbers k such that phi(sigma(k)+k) = sigma(k-phi(k)), where phi is A000010 and sigma is A000203.

10, 22, 38, 58, 82, 182, 228, 244, 308, 346, 404, 446, 514, 524, 644, 922, 1020, 1214, 1484, 1522, 1538, 1582, 2104, 2408, 5600, 5924, 7596, 8420, 13352, 13378, 13738, 14686, 15012, 20128, 21272, 27084, 27580, 29312, 37158, 43946, 47284, 47468

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..350

MATHEMATICA

Select[Range[50000], EulerPhi[DivisorSigma[1, #]+#]==DivisorSigma[1, #-EulerPhi[ #]]&] (* Harvey P. Dale, Sep 09 2022 *)

PROG

(PARI) s(n) = sigma(n-eulerphi(n)); e(n) = eulerphi(sigma(n)+n); j = []; for(n = 1, 10^5, if(e(n) == s(n), j = concat(j, n))); j

(PARI) { n=0; for (x=2, 10^9, if (eulerphi(sigma(x) + x) == sigma(x - eulerphi(x)), write("b063710.txt", n++, " ", x); if (n==350, break)) ) } \\ Harry J. Smith, Aug 28 2009

CROSSREFS

Sequence in context: A177791 A028569 A014367 * A157917 A242234 A104867

Adjacent sequences: A063707 A063708 A063709 * A063711 A063712 A063713

KEYWORD

easy,nonn

AUTHOR

Jason Earls, Aug 23 2001

STATUS

approved