cp's OEIS Frontend

A229687 Odd squares whose binary reversal is also a square.

%I A229687 #36 Dec 21 2013 03:05:46
%S A229687 1,9,20457529,143784081,331130809,4365905625,5216450625,20074072489,
%T A229687 1193532215121,10036851273801,36014509461681,38767247532225,
%U A229687 41413201925481,155991531977649,320642706437001,2543173099393689,2696589987547401,4665141483989281,87463589042698969
%N A229687 Odd squares whose binary reversal is also a square.
%C A229687 The sequence of binary reversals that are squares is a permutation of a(n), it begins: 1, 9, 20457529, 143784081, 331130809, 5216450625, 4365905625, 20074072489, 1193532215121, 10036851273801, 38767247532225, 36014509461681, ...
%C A229687 A029983 is a subsequence (after zero). - _Antti Karttunen_, Dec 20 2013
%F A229687 a(n) = A229766(n)^2.
%o A229687 (C)
%o A229687 #include <stdio.h>
%o A229687 #include <math.h>
%o A229687 int main() {
%o A229687   unsigned long long n, t, r, sr;
%o A229687   for (n=1; n<(1ULL<<32); n+=2) {
%o A229687      t = n*n;
%o A229687      r = 0;
%o A229687      while (t)  r = r*2+(t&1),  t >>= 1;
%o A229687      sr = sqrt(r);
%o A229687      if (sr*sr==r)  printf("%llu, ", n*n);
%o A229687   }
%o A229687   return 0;
%o A229687 }
%o A229687 (Scheme) (define (A229687 n) (A000290 (A229766 n))) ;; _Antti Karttunen_, Dec 20 2013
%Y A229687 Cf. A000290, A029983, A074832, A229766.
%K A229687 nonn,base
%O A229687 1,2
%A A229687 _Alex Ratushnyak_, Dec 19 2013