A118252 The least positive integer whose reversed binary representation does not occur in the concatenation of the reversed binary representations of all preceding terms.

1, 2, 3, 4, 8, 10, 11, 12, 15, 16, 22, 24, 27, 32, 35, 36, 38, 43, 44, 54, 59, 64, 66, 70, 76, 79, 83, 85, 88, 91, 95, 97, 99, 116, 122, 127, 128, 130, 132, 136, 140, 147, 148, 150, 155, 158, 163, 169, 170, 175, 176, 179, 182, 184, 192, 196, 201, 217, 232

Offset: 1

Author

Leroy Quet, Apr 18 2006

Keywords

• easy
• nonn

Comments

See the variant A118250 for comments and examples.

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A118248 (variant without reversal), A118250 (the same with a(0)=0), A118251 (concatenation of terms in binary).

Cf. A190896.

Programs

Mathematica

a = {1}; b = {1}; Do[k = b[[i - 1]] + 1; While[SequenceCount[Flatten@ a, Set[d, Reverse@ IntegerDigits[k, 2]]] != 0, k++]; a = Join[a, d]; AppendTo[b, k], {i, 2, 59}]; b (* Michael De Vlieger, Aug 21 2017 *)

PARI

A118252(n,show=0,a=1)={my(c=[a],S=[],L); for(k=1,n, show & print1(a","); while( setsearch(S,binary(a++)),); c=concat(binary(a),c); S=[]; for(i=0,#c-L=#binary(a), c[i+1] & for(j=i+L,min(i+L+1,#c), S=setunion(S,Set(t=[vecextract(c,2^j-2^i)])))));a}  \\ M. F. Hasler, Dec 29 2012

Extensions

More terms from Graeme McRae, Apr 19 2006

Explicit definition from M. F. Hasler, Dec 29 2012