cp's OEIS Frontend

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.

A343566 Numbers k such that A343564(k) is divisible by 2*k.

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%I A343566 #8 Apr 26 2021 01:47:32
%S A343566 1,2,3,24,63,107,263,383,504,75414,17389821,47574810
%N A343566 Numbers k such that A343564(k) is divisible by 2*k.
%e A343566 a(4) = 24 is a term because A343564(24) = 96 is divisible by 2*24 = 48.
%p A343566 N:= 100000: # for terms <= N
%p A343566 P:= select(isprime,[seq(i,i=3..2*N)]):
%p A343566 f:= proc(n) local m,Q,q;
%p A343566   m:= ListTools:-BinaryPlace(P,2*n);
%p A343566   Q:= convert(P[1..m],set);
%p A343566   Q:= Q intersect map(t -> 2*n-t, Q);
%p A343566   add(2*n mod q, q = Q);
%p A343566 end proc:
%p A343566 A343564:= map(f, [$1..N]):
%p A343566 select(t -> A[t] mod (2*t) = 0, [$1..N]);
%Y A343566 Cf. A343564.
%K A343566 nonn,more
%O A343566 1,2
%A A343566 _J. M. Bergot_ and _Robert Israel_, Apr 20 2021
%E A343566 a(11) and a(12) from _Martin Ehrenstein_, Apr 25 2021