This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A161444 #4 Jan 25 2018 09:54:59 %S A161444 4,21,38,55,64,81,98,115,140,157,174,191,200,217,234,251,261,276,295, %T A161444 310,321,336,355,370,397,412,431,446,457,472,491,506,518,535,548,565, %U A161444 578,595,608,625,654,671,684,701,714,731,744,761,775,790,805,820,835 %N A161444 Numbers n such that A160700(n) = 4. %H A161444 Charles R Greathouse IV, <a href="/A161444/b161444.txt">Table of n, a(n) for n = 1..10000</a> %F A161444 16n - 16 <= a(n) <= 16n - 1. - _Charles R Greathouse IV_, Jan 25 2018 %o A161444 (PARI) A160700(n)=my(t=n%16); while(n>15, n>>=4; t=bitxor(t, n%16)); t %o A161444 a(n)=for(k=16*n-16, 16*n-1, if(a(k)==4, return(k))) \\ _Charles R Greathouse IV_, Jan 25 2018 %Y A161444 A161440, A161441, A161442, A161443, A161445, A161446, A161447, A161448, A161449, A161450, A161451, A161452, A161453, A161454, A161455. %K A161444 nonn,easy %O A161444 1,1 %A A161444 _Reinhard Zumkeller_, Jun 10 2009