cp's OEIS Frontend

A182580 Position of first occurrence of n in A182576.

%I A182580 #10 May 07 2012 14:07:44
%S A182580 0,1,2,5,11,27,29,46,76,167,133,348,521,1160,1364,3005,3571,9348,9349,
%T A182580 20820,24476,64062,64079,123651,167761,439203,439204,1149850,1149851,
%U A182580 3010348,3010349,7881195,7881196,20633238,20633239,54018520,54018521,141422323,141422324
%N A182580 Position of first occurrence of n in A182576.
%C A182580 Conjecture: for k > 12, a(2k) = a(2k-1) + 1.
%e A182580 First occurrence of 4 in A182576(n) has index 11, so a(4)=11.
%o A182580 (C)
%o A182580 #include <stdio.h> // GCC // ~880 secs
%o A182580 typedef unsigned long long U64;
%o A182580 U64 fibs[992], first[992], prpr=0, prev=1, current, n, sq;
%o A182580 long long ftop, fpos, terms;
%o A182580 int main(int argc, char **argv)
%o A182580 {
%o A182580     for (ftop=0; ftop<900; ++ftop) {
%o A182580       fibs[ftop] = current = prpr+prev;
%o A182580       if (current<prev) break;
%o A182580       prpr = prev,  prev = current;
%o A182580     }
%o A182580     printf("%llu\n%llu\n%llu\n%llu\n",ftop,prev,prpr,(U64)-1-prev);
%o A182580     for (n=0; n < ((U64)1<<32); ++n) {
%o A182580         fpos=ftop-1, terms=0;
%o A182580         for (sq=n*n; sq>0 && fpos>=0; ++terms, sq-=fibs[fpos], --fpos) {
%o A182580                 while (fibs[fpos]>sq && fpos>0) --fpos;
%o A182580         }
%o A182580         if (sq>0) { printf("Error!"); exit(1); }
%o A182580         if (first[terms]==0)
%o A182580             first[terms]=n, printf("%2llu %llu\n",terms,n);
%o A182580     }
%o A182580     for (n=0; n<ftop; ++n)  printf("%llu, ", first[n]);
%o A182580     return 0;
%o A182580 }
%Y A182580 Cf. A182576.
%K A182580 nonn
%O A182580 0,3
%A A182580 _Alex Ratushnyak_, May 05 2012