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A299535 Solutions to A000010(x) + A000010(x-1) = A000010(2*x). 2
2, 4, 16, 256, 496, 976, 2626, 3256, 3706, 5188, 11716, 13366, 18316, 22936, 25546, 46216, 49216, 49336, 57646, 65536, 164176, 184636, 198316, 215776, 286996, 307396, 319276, 388246, 397486, 415276, 491536, 568816, 589408, 686986, 840256, 914176, 952576, 983776 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Terms are even. Does lim_{n -> infty} log(a(n))/log(n) exist?

Are all terms except 2 congruent to 4 (mod 6)? - Robert Israel, Feb 27 2018

Includes the Fermat numbers 2^(2^j)+1 for j = 0 .. 5, but no other members of A019434. - Benoit Cloitre, corrected by Robert Israel, Mar 02 2018

Even numbers n for which A000010(n) = A000010(n-1). - Robert Israel, Mar 02 2018

LINKS

Robert Israel, Table of n, a(n) for n = 1..100

Benoit Cloitre, Plot of log(a(n))/log(n+1) for n=1 up to 62

MAPLE

select(t -> numtheory:-phi(t)+ numtheory:-phi(t-1)=numtheory:-phi(2*t), [seq(i, i=2..10^6, 2)]); # Robert Israel, Feb 27 2018

PROG

(PARI) for(n=2, 200000, if(eulerphi(n) + eulerphi(n-1) == eulerphi(2*n), print1(n, ", ")))

(MAGMA) [n: n in [2..10^6] | EulerPhi(n)+EulerPhi(n-1) eq EulerPhi(2*n)]; // Bruno Berselli, Feb 27 2018

CROSSREFS

Cf. A000010.

Sequence in context: A105788 A217727 A071008 * A220169 A178077 A218148

Adjacent sequences:  A299532 A299533 A299534 * A299536 A299537 A299538

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Feb 27 2018

EXTENSIONS

More terms from Robert Israel, Feb 27 2018

STATUS

approved

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Last modified July 8 02:24 EDT 2020. Contains 335503 sequences. (Running on oeis4.)