cp's OEIS Frontend

A228087 a(n) = largest k which satisfies n = k + bitcount(k), or 0 if no such k exists. Here bitcount(k) (A000120) gives the number of 1's in binary representation of nonnegative integer k.

%I A228087 #11 Oct 12 2013 22:00:13
%S A228087 0,0,1,2,0,4,0,5,6,8,7,9,10,0,12,0,13,16,0,17,18,0,20,0,21,22,24,23,
%T A228087 25,26,0,28,0,32,30,33,34,0,36,0,37,38,40,39,41,42,0,44,0,45,48,0,49,
%U A228087 50,0,52,0,53,54,56,55,57,58,0,60,64,61,65,66,63,68,0
%N A228087 a(n) = largest k which satisfies n = k + bitcount(k), or 0 if no such k exists. Here bitcount(k) (A000120) gives the number of 1's in binary representation of nonnegative integer k.
%C A228087 A083058(n)+1 gives a lower bound for nonzero terms, n-1 an upper bound.
%H A228087 Antti Karttunen, <a href="/A228087/b228087.txt">Table of n, a(n) for n = 0..8192</a>
%H A228087 <a href="/index/Coi#Colombian">Index entries for Colombian or self numbers and related sequences</a>
%o A228087 (Scheme) (define (A228087 n) (let loop ((k n)) (cond ((<= k (A083058 n)) 0) ((= n (A092391 k)) k) (else (loop (- k 1))))))
%Y A228087 Cf. A228086, A228085. A010061 gives the positions of zeros after a(0). The union of A010061 and A228088 gives the positions where a(n) = A228086(n).
%Y A228087 Cf. also A213724, A227643.
%K A228087 nonn
%O A228087 0,4
%A A228087 _Antti Karttunen_, Aug 09 2013