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 A282090 Totient numbers (A002202) of the form 1 + k + k^2 + k^3 +...+ k^i (i > 1, k > 1). 1

%I

%S 40,156,400,820,1464,2380,3280,3616,3906,5220,7240,9724,12720,19608,

%T 20440,25260,30784,37060,60880,66430,70644,81400,93196,97656,106080,

%U 120100,135304,151740,169456,177156,188500,254080,265720,278916,333340,363024,394420,427576,462540,499360

%N Totient numbers (A002202) of the form 1 + k + k^2 + k^3 +...+ k^i (i > 1, k > 1).

%C Totient numbers of the form (k^(i+1) - 1)/(k - 1) where k and i are both odd numbers that are greater than 1.

%H Charles R Greathouse IV, <a href="/A282090/b282090.txt">Table of n, a(n) for n = 1..10000</a>

%e 40 is a term because 1 + 3 + 9 + 27 = 40 is a totient number.

%o (PARI) list(lim)=my(v=List(), e, t); for(b=2, sqrt(lim), e=3; while((t=(b^e-1)/(b-1))<=lim, if(istotient(t),listput(v, t)); e++)); vecsort(Vec(v), , 8) \\ _Ray Chandler_, Feb 08 2017

%Y Intersection of A002202 and A053696.

%Y Cf. A281962.

%K nonn

%O 1,1

%A _Altug Alkan_, Feb 06 2017

%E Terms confirmed by _Ray Chandler_, Feb 08 2017

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Last modified January 20 13:06 EST 2022. Contains 350472 sequences. (Running on oeis4.)