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 A070418 Numbers k such that k and phi(k) have the same number of divisors. 4
 1, 3, 14, 15, 22, 28, 44, 46, 50, 56, 68, 70, 78, 88, 92, 94, 110, 112, 118, 166, 174, 176, 184, 188, 198, 214, 224, 228, 230, 234, 236, 255, 260, 294, 306, 318, 332, 334, 342, 352, 358, 368, 376, 414, 428, 448, 454, 462, 470, 472, 492, 500, 526, 550, 580, 590 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS This is an infinite sequence; for example, 2^(m-1)*5^m is in the sequence for all m >= 2. See Bellaouar et al. 2023. - Allen Stenger, Feb 16 2024 LINKS G. C. Greubel, Table of n, a(n) for n = 1..8407 (for values up to 500000) Djamel Bellaouar, Abdelmadjid Boudaoud and Rafael Jakimczuk, Notes on the equation d(n) = d(phi(n)) and related inequalities, Math. Slovaca 73 (2023), no. 3, 613-632. MATHEMATICA Select[Range[600], DivisorSigma[0, #]==DivisorSigma[0, EulerPhi[#]]&] (* Harvey P. Dale, Sep 04 2015 *) PROG (PARI) for(n=1, 900, if(numdiv(n)==numdiv(eulerphi(n)), print1(n, ", "))) CROSSREFS Cf. A000005, A000010 (phi), A116518 (odd terms). Sequence in context: A171653 A055435 A242868 * A178363 A294997 A354740 Adjacent sequences: A070415 A070416 A070417 * A070419 A070420 A070421 KEYWORD easy,nonn AUTHOR Benoit Cloitre, May 12 2002 STATUS approved

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Last modified April 23 06:04 EDT 2024. Contains 371906 sequences. (Running on oeis4.)