A340384 - OEIS

%I #15 Jan 16 2021 06:40:02

%S 42,70,154,176,182,238,266,322,406,434,518,574,602,658,742,826,854,

%T 938,994,1022,1106,1162,1246,1250,1358,1414,1442,1498,1526,1582,1664,

%U 1778,1834,1918,1946,2086,2114,2198,2282,2338,2422,2506,2534,2674,2702,2758,2786,2954,3122,3178,3206,3262,3346,3374,3514,3598

%N Positions of seventeens in A340094, the Dirichlet inverse of f(n) = n - phi(n) + 1.

%C These terms correspond to the horizontal line shown above the X-axis in the logarithmic scatter plots of A340094.

%C The only non-multiples of 7 among the first 13832 terms are 176, 1250, 1664. Apart from such exceptions (are there more?), all other terms are of the form 2*7*p, with p running through all odd primes in A065091 \ {7}.

%H Antti Karttunen, <a href="/A340384/b340384.txt">Table of n, a(n) for n = 1..13832; all terms < 2^21</a>

%F {n such that A340094(n) = 17}.

%o (PARI) isA340384(n) = (17==A340094(n));

%Y Cf. A065091, A340094.

%K nonn

%O 1,1

%A _Antti Karttunen_, Jan 07 2021