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 A115420 #14 Mar 29 2024 02:22:51 %S A115420 16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,48,49,50,51,52,53,54, %T A115420 55,56,57,58,59,60,61,62,63,80,81,82,83,84,85,86,87,88,89,90,91,92,93, %U A115420 94,95,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127 %N A115420 Numbers having a 1 in position 4 of their binary expansion. %C A115420 One of the mystery calculator sequences: A005408, A042964, A047566, A115419, A115420, A115421. %H A115420 Edd Mann, <a href="https://eddmann.com/mystery-calculator-clojurescript/">Mystery Calculator</a>. %e A115420 a(1) = 16 = 10000 in binary. %p A115420 a:= n-> n+15 + 16*iquo(n-1, 16): %p A115420 seq(a(n), n=1..100); # _Alois P. Heinz_, Aug 22 2011 %o A115420 (Python) %o A115420 def A115420(n): return ((n-1<<1)&-15|16)+(n-1&15) # _Chai Wah Wu_, Mar 28 2024 %Y A115420 Cf. A005408, A042964, A047566, A115419, A115421. %K A115420 base,easy,nonn %O A115420 1,1 %A A115420 _Jeremy Gardiner_, Jan 22 2006