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 A028836 #13 Jul 08 2025 18:53:50 %S A028836 1,2,4,8,10,11,13,17,19,20,22,26,28,29,31,35,37,38,40,44,46,47,49,53, %T A028836 55,56,58,62,64,65,67,71,73,74,76,80,82,83,85,89,91,92,94,98,100,101, %U A028836 103,107,109,110,112,116,118,119,121,125,127,128,130,134,136,137,139,143,145,146,148,152,154,155 %N A028836 Iterated sum of digits of n is a power of 2. %F A028836 Conjectures from _Colin Barker_, Feb 10 2020: (Start) %F A028836 G.f.: x*(1 + x + 2*x^2 + 4*x^3 + x^4) / ((1 - x)^2*(1 + x)*(1 + x^2)). %F A028836 a(n) = a(n-1) + a(n-4) - a(n-5) for n>5. %F A028836 (End) %F A028836 This g.f. follows from the observation that a(n+4) = a(n)+9 and this holds since the iterated sum of digits of N equals the iterated sum of digits of N+9. - _Peter Bala_, Feb 10 2020 %Y A028836 Cf. A010888, A028838, A028889. %K A028836 nonn,base %O A028836 1,2 %A A028836 _N. J. A. Sloane_ %E A028836 More terms from Scott Lindhurst (ScottL(AT)alumni.princeton.edu) %E A028836 Checked by Neven Juric (neven.juric(AT)apis-it.hr), Feb 04 2008