A067799 - OEIS

A067799

Numbers k such that phi(k) + phi(k+1) = sigma(k).

2, 3, 5, 115, 143, 287, 371, 413, 623, 791, 4067, 10031, 24149, 32335, 39689, 88403, 93443, 107365, 148735, 168833, 212993, 427763, 555947, 650095, 925253, 1017821, 1117457, 1139467, 1229327, 1270801, 1407295, 2184221, 2294509, 2913757, 3258355, 4699981, 5747291

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OFFSET

1,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..138

MATHEMATICA

Select[Range[10^6], EulerPhi[#] + EulerPhi[# + 1] == DivisorSigma[1, #] &] (* Amiram Eldar, May 21 2022 *)

CROSSREFS

Cf. A000010, A000203, A092404.

Sequence in context: A111331 A205668 A118505 * A321362 A230372 A234900

Adjacent sequences: A067796 A067797 A067798 * A067800 A067801 A067802

KEYWORD