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 A182187 a(n) is the least m >= n such that the Hamming distance D(n,m) = 2. 7
 3, 2, 4, 5, 7, 6, 10, 11, 11, 10, 12, 13, 15, 14, 22, 23, 19, 18, 20, 21, 23, 22, 26, 27, 27, 26, 28, 29, 31, 30, 46, 47, 35, 34, 36, 37, 39, 38, 42, 43, 43, 42, 44, 45, 47, 46, 54, 55, 51, 50, 52, 53, 55, 54, 58, 59, 59, 58, 60, 61, 63, 62, 94, 95, 67, 66, 68 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS a(n) = n<+>2 (see comment in A206853). LINKS Alois P. Heinz, Table of n, a(n) for n = 0..1000 FORMULA If n is odd, then a(n) = n+2^(A007814(n+1)-1); if n == 2 (mod 4), then a(n) = n+2^(A007814(n+2)-1); if n == 0 (mod 4), then a(n) = n+3. Using this formula, we can prove the conjecture formulated in comment in A209554 in the case k=2. Moreover, let us show that if N does not have the form 8*t or 8*t+1, then it can be represented in the form n<+>2. Indeed, in the cases N = 8*t+2, 8*t+4, 8*t+6, 8*t+3, 8*t+5 and 8*t+7 it is sufficient to choose n=N-4, n=N-2, n=N-1, n=N-3, n=N-2 and n = N-3 respectively; in the cases 8*t, 8*t+1, for every choice of n <= N, we do not obtain the equality n<+>2 = N. In addition, note that n<+>1 = n + 2^A007814(n+1) = A086799(n+1). MAPLE HD:= (i, j)-> add(h, h=Bits[Split](Bits[Xor](i, j))): a:= proc(n) local c;       for c from n do if HD(n, c)=2 then return c fi od     end: seq(a(n), n=0..100);  # Alois P. Heinz, Apr 17 2012 MATHEMATICA t={}; Do[i=n+1; While[Count[IntegerDigits[BitXor[n, i], 2], 1]!=2, i++]; AppendTo[t, i], {n, 0, 66}]; t (* Jayanta Basu, May 26 2013 *) PROG (Sage) def A182187(n):     S = n.bits(); T = S; c = n; L = len(S)     while true:          H = sum(a != b for a, b in zip(S, T))          if H == 2: return c          c += 1; T = c.bits()          if len(T) > L: L += 1; S.append(0) [A182187(n) for n in (0..66)]   # Peter Luschny, May 26 2013 (Python) def a(n):   m = n + 1   while bin(n^m).count('1') != 2: m += 1   return m print([a(n) for n in range(67)]) # Michael S. Branicky, Mar 02 2021 (PARI) a(n) = bitxor(n, 3<>1+1, 2)); \\ Kevin Ryde, Jul 09 2021 CROSSREFS Cf. A206853 (trajectory of 1), A207063 (trajectory of 0). Cf. A209544 (primes which are not terms), A209554 (and also not n<+>3). Cf. A086799 ((n-1)<+>1), A182209 (n<+>3), A182336 (n<+>4). Cf. A205509, A205510, A205511, A205302, A205649, A205533, A122565, A206852, A206960, A007814. Sequence in context: A056011 A117123 A116966 * A334652 A163241 A234027 Adjacent sequences:  A182184 A182185 A182186 * A182188 A182189 A182190 KEYWORD nonn,base,easy AUTHOR Vladimir Shevelev, Apr 17 2012 EXTENSIONS More terms from Alois P. Heinz, Apr 17 2012 STATUS approved

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Last modified September 28 01:47 EDT 2022. Contains 357063 sequences. (Running on oeis4.)