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 A181518 #16 Feb 15 2025 13:34:43
%S A181518 2,4,7,11,13,16,22,25,28,35,37,38,41,47,50,52,56,59,64,67,70,76,88,93,
%T A181518 97,98,100,117,122,133,137,140,143,148,158,171,176,179,182,186,193,
%U A181518 196,200,203,213,218,223,227,233,234,236,242,247,248,253,262,280,290,299
%N A181518 a(n) is the number for which 2^A181516(n)||(2*a(n))!
%C A181518 Numbers m such that Sum_{k >= 0} floor(m/2^k) is a prime. - _Clark Kimberling_, Feb 13 2025
%p A181518 isA011371 := proc(n) option remember; local k,a; for k from 0 do a := A011371(k) ; if a > n then return false; elif a = n then return true; end if; end do: end proc:
%p A181518 A181516 := proc(n) option remember; local a; if n = 1 then 3; else for a from procname(n-1)+1 do if isprime(a) then if isA011371(a) then return a; end if; end if; end do; end if; end proc:
%p A181518 A181518 := proc(n) for m from 1 do if A011371(m) = A181516(n) then return m/2 ; end if; end do: end proc: # _R. J. Mathar_, Nov 04 2010
%t A181518 f[n_] := Sum[Floor[n/2^k], {k, 0, Floor[Log[2, n]]}] (* A005187 *)
%t A181518 Select[Range[400], PrimeQ[f[#]] &] (* _Clark Kimberling_, Feb 13 2025 *)
%Y A181518 Cf. A000040, A005187.
%K A181518 nonn
%O A181518 1,1
%A A181518 _Vladimir Shevelev_, Oct 26 2010
%E A181518 Corrected (88 inserted, 129 replaced by 179) and extended beyond 227 by _R. J. Mathar_, Nov 04 2010