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.

A348852 Numbers k such that the number of odd nonprimes <= k is equal to the number of primes <= k.

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%I A348852 #9 Nov 07 2021 02:12:27
%S A348852 2,93,94,97,98,101,102,105,106,117,118
%N A348852 Numbers k such that the number of odd nonprimes <= k is equal to the number of primes <= k.
%C A348852 This sequence is finite. For k > 118, there are always more odd nonprimes than primes <= k.
%C A348852 Numbers k such that A000720(k) = A033271(k). - _Michel Marcus_, Nov 06 2021
%e A348852 a(4) = 97 is a term because there are 25 odd nonprimes <= 97 and 25 primes <= 97.
%t A348852 Select[Range@1000,(k=#;Length@Select[Range@k,OddQ@#&&!PrimeQ@#&]==PrimePi@k)&]
%o A348852 (PARI) isok(k) = primepi(k) == #select(x->(!isprime(x) && (x%2)), [1..k]); \\ _Michel Marcus_, Nov 06 2021
%Y A348852 Cf. A000040, A014076, A000720, A033271.
%K A348852 nonn,fini,full
%O A348852 1,1
%A A348852 _Giorgos Kalogeropoulos_, Nov 01 2021