A044453 - OEIS

%I #9 Nov 27 2021 04:52:31

%S 11,27,47,59,75,91,111,123,139,155,191,203,219,239,251,267,283,303,

%T 315,331,347,367,379,395,411,447,459,475,495,507,523,539,559,571,587,

%U 603,623,635,651,667,767,779,795,815,827,843,859,879,891,907,923,959,971

%N Numbers k such that string 2,3 occurs in the base 4 representation of k but not of k+1.

%H Michael S. Branicky, <a href="/A044453/b044453.txt">Table of n, a(n) for n = 1..10000</a>

%o (Python)

%o from sympy.ntheory.factor_ import digits

%o def has23(n): return "23" in "".join(map(str, digits(n, 4)[1:]))

%o def ok(n): return has23(n) and not has23(n+1)

%o print([k for k in range(972) if ok(k)]) # _Michael S. Branicky_, Nov 27 2021

%Y Cf. A044072.

%K nonn,base

%O 1,1

%A _Clark Kimberling_

%E a(48) and beyond from _Michael S. Branicky_, Nov 27 2021