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Largest natural number x such that x = n + A000120(x), or zero if no such number exists.
16

%I #16 Aug 19 2022 14:02:58

%S 1,3,0,5,7,0,0,9,11,0,13,15,0,0,0,17,19,0,21,23,0,0,25,27,0,29,31,0,0,

%T 0,0,33,35,0,37,39,0,0,41,43,0,45,47,0,0,0,49,51,0,53,55,0,0,57,59,0,

%U 61,63,0,0,0,0,0,65,67,0,69,71,0,0,73,75,0,77,79,0,0,0,81,83,0,85,87,0,0,89,91

%N Largest natural number x such that x = n + A000120(x), or zero if no such number exists.

%H Antti Karttunen, <a href="/A213724/b213724.txt">Table of n, a(n) for n = 0..1024</a>

%F a(0)=1; and for n>=1, a(n)=0 if A079559(n)=0 (i.e., if A213723(n)=0); otherwise A213723(n)+1.

%o (Scheme): (define (A213724 n) (if (zero? n) 1 (let ((v (A213723 n))) (if (zero? v) v (+ 1 v)))))

%o (Haskell)

%o a213724 0 = 1

%o a213724 n = a213723 n + signum (a213723 n)

%o -- _Reinhard Zumkeller_, May 01 2015

%Y One more than A213723 at its nonzero points. a(A005187(n)) = A005408(n). Used for computing A213725-A213727.

%Y Cf. A179016. - _M. F. Hasler_, Nov 01 2012

%K nonn

%O 0,2

%A _Antti Karttunen_, Nov 01 2012